Biodegradable endoprostheses and methods of their fabrication

ABSTRACT

A biodegradable stent prosthesis formed from a degradable material, having a plurality of luminal, abluminal, and side surface regions, wherein a surface portion extending between the abluminal and luminal surface region of at least some structural elements is convex.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/800,536, filed Jul. 15, 2015, which claims priority to U.S.Provisional Patent Application No. 62/187,737, filed on Jul. 1, 2015;this application is also a continuation-in-part of U.S. patentapplication Ser. No. 14/697,537, filed Apr. 27, 2015, which is acontinuation-in-part of U.S. patent application Ser. No. 14/682,014,filed Apr. 8, 2015, which is a continuation-in-part of U.S. patentapplication Ser. No. 14/461,159, filed Aug. 15, 2014, all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to medical devices and methodsfor their fabrication. In particular, the present invention relates tothe fabrication of biodegradable endoprostheses, such as stentprostheses, having shaped surface regions for enhanced implantationperformance, enhanced drug delivery or other enhanced properties.

Stents are generally tubular-shaped devices which function to hold openor reinforce a segment of a blood vessel or body lumen, such as acoronary artery, carotid artery, saphenous vein graft, or femoralartery. They also are suitable to support and hold back a dissectedarterial lining that could otherwise occlude the body lumen, tostabilize plaque, or to support/hold open a bioprosthetic valves. Stentscan be formed from various materials, particularly polymeric and/ormetallic materials, and may be non-degradable or biodegradable. Stentsare typically delivered to the target area within the body lumen using acatheter. With balloon-expandable stents, the stent is mounted onto aballoon catheter, navigated to the appropriate area, and the stent isexpanded by inflating the balloon. A self-expanding stent is deliveredto the target area and released, expanding to treat the disease.

Of particular interest to the present invention are biodegradablestents, including polymer stents, such as biodegradable polymer stentsor also called scaffolds and other endoprostheses. Biodegradable stentsare usually formed from polymers which degrade by various mechanismssuch as by hydrolysis and other reaction mechanisms in the vascular orother body environment. This invention also applies to metallicbiodegradable stents.

Biodegradable polymer implantable devices and methods of making them arealso described in commonly owned U.S. Pat. Nos. 8,182,890; 8,323,760;8,636,792; 8,814,930; and U.S. Patent Publication Nos. 2008/0177373 and2006/0029711 the entire disclosure of each of which is incorporatedherein by reference.

BRIEF SUMMARY OF THE INVENTION

In embodiments of the disclosure an expandable biodegradable stentprosthesis comprises: a tubular expandable stent prosthesis bodycomprising a biodegradable material, for example a polymericbiodegradable material, said expandable stent prosthesis body comprisingstent structural elements each having a luminal surface region and anabluminal surface region and a thickness between said luminal andabluminal surface regions; wherein a region extending between theabluminal surface region and the luminal surface region of at least somestructural elements is bulbous.

In some embodiments two side surface regions extending between theluminal and abluminal surface regions of at least some stent structuralelements are bulbous.

In embodiments of the disclosure an expandable biodegradable stentprosthesis comprises: an expandable stent prosthesis body comprising abiodegradable polymeric material, wherein the stent comprises aplurality of stent structural elements, wherein said stent structuralelements each have a luminal surface region, an abluminal surfaceregion, and two side surface regions extending between the luminal andabluminal surface regions; and wherein at least some of the stentstructural elements have a bulbous shape coupling said abluminal andsaid luminal surface regions to form a dogbone shaped cross section.

In embodiments of the disclosure an expandable biodegradable stentprosthesis comprises: a tubular expandable stent prosthesis bodycomprising a biodegradable polymeric material, said expandable stentprosthesis body comprising stent structural elements each having aluminal surface region and an abluminal surface region and a thicknessbetween said luminal and abluminal surface regions; wherein thethickness varies across the width of at least some of the structuralelements.

In embodiments of the disclosure an expandable biodegradable stentprosthesis comprises a tubular expandable stent prosthesis body formedfrom a biodegradable, for example polymeric, material, said expandablestent prosthesis body comprising stent structural elements havingluminal and abluminal surface regions; wherein at least some of the bodyabluminal surface regions are concave or flat across substantially theirwidth. Said stent prosthesis may be expandable from a crimpedconfiguration to an expanded larger configuration to support a bloodvessel. At least some or substantially all of the side surface regionsmay be substantially convex. At least some or substantially all of theside surface regions which in use face the distal end of the deliverycatheter may be substantially convex or completely convex.

The stent structural elements may for example comprise struts andcrowns. The struts and crowns may each have an abluminal surface regionand a luminal surface region. The stent structural elements may comprisestruts, crowns, and links, each having an abluminal surface region and aluminal surface region. Each strut, crown, and link may have anabluminal surface region, a luminal surface region, and two side surfaceregions extending between the abluminal and luminal surface regions.

The expandable stent prosthesis body may comprise expandable serpentinerings, each ring may be composed of struts joined by crowns, and eachring may be connected to an adjacent ring by at least one link.

The struts and crowns may have two side surface regions extendingbetween the luminal and abluminal surface regions, wherein at least someof the side surface regions are convex.

The expandable prosthesis may be formed of a biodegradable polymericmaterial which comprises at least two biodegradable polymers.

The expandable prosthesis body may have been treated to form the concaveabluminal surface regions.

In embodiments of the disclosure an expandable biodegradable stentprosthesis comprises a tubular expandable stent prosthesis bodycomprising a biodegradable, for example polymeric material, saidexpandable stent prosthesis body comprising stent structural elementshaving luminal and abluminal surface regions; wherein at least some ofthe side surface regions are convex across substantially the thicknessof said side surface regions. Said stent prosthesis may be expandablefrom a crimped configuration to an expanded larger configuration tosupport a blood vessel. Substantially all of the side surface region maybe convex. At least some or substantially all of the side surfaceregions which in use face the distal end of the delivery catheter may beconvex. At least some or substantially all of the abluminal surfaceregions may be concave, flat or straight, substantially across theirwidth.

The convex side surface regions and concave, flat or straight abluminalsurface regions may be prepared by treating to shape the stentstructural elements or may be formed to have the desired shapes. Thetreatment may comprise shaping by application of a solvent by at leastone of dipping, spraying, or contact with a solvent vapor. The treatmentmay alternatively or additionally comprise shaping by at least one oftumbling, agitating, deburring, scraping, media blasting, lasertreatment and heat treatment.

The treatment may not significantly dissolve (or permanently remove) thepolymeric material from which said prosthesis is formed. For example,the treatment may shift material from one stent structural element (alsoreferred to herein as a stent structure) to an adjacent surface regionof the same or different stent structural element without a substantialchange in body weight or mass of said expandable stent prosthesis. Theapplication of the solvent may soften the polymeric material allowing itto move, flow or redistribute from one surface region to another surfaceregion on the stent structural elements without the polymeric materialbecoming dissolved in (or otherwise dispersed in) in the solvent.

The expandable stent prosthesis body may have been patterned from a tubeby a laser. The expandable stent may have been patterned from asubstantially continuous tubular body, substantially free fromdiscontinuities or substantially free from holes.

The expandable stent prosthesis body may have been patterned from a tubeby a laser and the stent structural elements treated to form the concaveabluminal surface regions and convex side surface regions.

A coating comprising at least one drug may be formed over at least someportions of the expandable stent prosthesis body.

The stent prosthesis may further comprise a coating over the expandablestent prosthesis body with the coating such that concave surface regionsof said stent structural elements remain substantially concave andconvex surface regions of said stent structural elements remainsubstantially convex. Whatever shape the surface region has may remainsubstantially the same shape after the coating.

A weight or mass of the expandable stent prosthesis after treatment maybe substantially the same as before treatment.

The biodegradable polymeric material may have an elastic modulus of atleast 0.35 GPa.

The biodegradable polymeric material may comprise one or more ofpolymers and copolymers.

The prosthesis may be capable of being expanded from a crimped diameterto a deployed diameter at body temperature without fracture.

The prosthesis may be capable of being expanded from a crimped diameterto a deployed diameter at body temperature without substantial rotationof at least one of the stent structural elements about their axis.

The biodegradable polymeric material may comprise at least one materialselected from the group consisting of lactides, poly-DL-Lactide,polylactide-co-gycolide, polylactide-co-polycaprolactone, poly(L-lactide-co-trimethylene carbonate), polytrimethylene carbonate,polyhydroxybutyrate, polyhydroxyvalerate, poly orthoesters, polyanhydrides, polylactide, polyglycolides, polycaprolactone,polyiminocarbonates and copolymers thereof.

The prosthesis may be balloon expandable.

The biodegradable polymeric material may have a molecular weight from100 KDa to 1000 KDa.

The body may have been treated to adjust a thickness of at least one ofthe stent structural elements from a first thickness before treatment toa second thickness after treatment, wherein the second thickness isgreater than the first thickness and the second thickness may varyacross the width of the stent structural element.

The body may have been treated to cause a thickness of a plurality ofstent structural elements between the luminal and abluminal surfaceregions to increase while a width of the stent structural elementsbetween the side surface regions remains substantially the same.

The body may be treated by exposing the expandable prosthesis to asolvent for a predetermined period of time to provide at least somesubstantially convex side surface regions and at least some concaveabluminal surface regions of said stent structural elements.

The body may have been treated to cause a thickness of the plurality ofstent structural elements between the luminal and abluminal surfaceregions to increase while decreasing a minimum width of the stentstructural elements between the side surface regions by redistributingthe polymeric material.

In an embodiment, a stent prosthesis comprises a tubular expandablestent prosthesis body formed from a biodegradable material, such as apolymeric material, said material is patterned into a stent radiallyexpandable from a crimped diameter to a deployed larger configuration,wherein the stent comprises a plurality of stent structural elements,such as struts joined by crowns, wherein said stent structural elementseach have a luminal surface region, an abluminal surface region, and twoside surface regions extending between the luminal and abluminal surfaceregions; and wherein at least some of the side surface regions have aconvex shape across substantially the thickness of said side surfaceregions; said stent prosthesis in the deployed diameter has sufficientstrength to support a blood vessel. The stent may comprise a pluralityof stent structural elements such as struts joined by crowns where atleast some of the crowns are connected to adjacent crowns by links orwhere at least some of the crowns are connected to adjacent crowns.

At least some of the stent structural element abluminal surface regionsmay have a concave shape across substantially their width. At least someof the stent structural element abluminal surface regions may have asurface shape similar to the surface of a dogbone, that is, acombination of convex and concave shapes across the width of theabluminal surface region.

Substantially all of the side surface regions may have a convex shapeacross substantially the thickness of said side surface regions.

The prosthesis may have been treated by contact with a solvent toredistribute said polymeric material to provide said concave or convexsurface regions as the case may be.

The prosthesis may have been treated by contact with a solvent to flowsaid polymeric material to provide said concave or convex surfaceregions as the case may be.

In embodiments of the disclosure an expandable biodegradable stentprosthesis comprises a tubular expandable stent prosthesis bodycomprising a biodegradable metal or metal alloy, such as zinc,magnesium, and iron, and alloys thereof, wherein the stent is treated tomodify at least some abluminal surface regions making them concavesubstantially across the width of said abluminal surface regions, and/orto modify at least some of side surface regions making themsubstantially convex across the thickness of said side surface regions.The above surface region modifications may be provided without asubstantial change in weight or mass compared to before treatment, orwithout losing more than 15% in weight or mass after treatment, orwithout losing more than 25% in weight or mass after treatment. Themetallic tubular body may be substantially continuous or substantiallyfree from discontinuities or substantially free from holes beforepatterning.

The prosthesis may have been treated by contact with a solvent toredistribute said polymeric material to vary the thickness of at leastone stent structural element and/or to vary the width of at least onestent structural element, for example to provide at least one stentstructural element with a width that is larger away from than close tosaid abluminal and luminal surface regions and/or with a thickness thatis smaller away from than close to the side surface regions.

In embodiments of the disclosure an expandable biodegradable stentprosthesis comprises a tubular expandable stent prosthesis bodycomprising a biodegradable polymeric material, wherein the tubular bodyhas an initial diameter, which may be larger than an intended deployeddiameter (labeled or nominal diameter) of the stent prosthesis (may be1.1-1.5 times larger than intended deployed diameter). The tubular bodymay be patterned with a laser or by etching to provide stent structuralelements, with the patterning preferably occurring at the initialdiameter that is 1.1-1.5 times the intended deployed diameter. Afterpatterning, some or all of the stent structural elements may be treatedto provide a convex shape to at least some of the side surface regionsand optionally a flat or concave shape to at least some of the abluminalsurface regions. Said treatment may be performed at substantially theas-formed (initial) tubular diameter, The stent prosthesis may betreated by heating the polymeric material above Tg (the glass transitiontemperature) and below Tm (the melting point) of said polymeric materialbefore or/and after the patterning of the stent prosthesis to provide ormodify various physical properties of the resulting stent prosthesis.The stent structural elements may be heated to above Tg and below Tm ofthe polymeric material after said shaping treatment but before beingcrimped to a smaller diameter. The stent prosthesis is capable of beingradially expanded or/and radially crimped and following insertion of thecrimped prosthesis may be expanded to a deployed to a diameter largerthan the crimped diameter to support a blood vessel or other body lumenwithout fracture.

In disclosed embodiments, a stent is formed from a substantiallycontinuous body (or a body at least substantially free from holes and/ordiscontinuities), said body has been patterned into a stent bodycomprising stent structural elements each having at least two surfaceregions, said at least two surface regions are an abluminal surfaceregion and a luminal surface region, wherein said stent structuralelements have a thickness, wherein said thickness of at least some stentstructural elements is variable across the width of said stentstructural elements, wherein the thickness extends between the abluminalsurface and luminal surface regions of a said stent structural elementwhich may have a convex shape. In preferred embodiments, at least somestructural elements have a larger thickness at about an end of theirabluminal surface region than about a midpoint of their abluminalsurface region. In some embodiments, the thickness at about an end of anabluminal region is smaller than that about a midpoint of the abluminalsurface region. In preferred embodiments, the cross section of at leastsome stent structural elements is oval, or dogbone shape. In someembodiments, the maximum stent structural element thickness is at least1.05 times the minimum stent structural element thickness. In someembodiments, the maximum stent structural element thickness rangesbetween 1.05-1.3 times the minimum stent structural element thickness.The minimum stent structural element thickness generally occurs near acenter of the abluminal surface region.

In some embodiments, a stent is formed from a substantially continuousbody (that is a body that is at least substantially free from holesand/or discontinuities), said body has been patterned into a stent bodycomprising stent structural elements each having at least two surfaceregions, said at least two surface regions are an abluminal surfaceregion and a luminal surface region, wherein said structural elementshave a thickness, wherein the surface area extending between theabluminal surface and luminal surface regions of the at least some stentstructural elements is convex. In some embodiments, the abluminalsurface region is substantially concave or substantially flat across thewidth of said stent structural element. In preferred embodiments, thecross section of at least some stent structural elements is oval ordogbone shape.

In a preferred embodiment, a degradable stent is formed from asubstantially continuous body comprising a polymeric material, formed byextrusion, dipping, spraying, or molding, said body has been patternedafter forming into a stent body comprising stent structural elementssaid structural elements comprising two surface regions, an abluminalsurface region and a luminal surface region, wherein said structuralelements have a thickness, wherein the region extending across thethickness between the abluminal surface and luminal surface regions ofthe at least some stent structural elements is bulbous in shape. Thestent prosthesis may have a thickness that varies across the width ofsaid structural elements. The stent prosthesis structural elements mayhave at least one side surface region wherein the side surface region isconvex across substantially the thickness of said structural elements.The stent prosthesis abluminal surface region may have a concave shapeacross substantially the width of said structural elements or the widthof the abluminal surface, said abluminal surface region may have abulbous region about an end region or towards an end region of saidstructural element width, wherein said bulbous region may have a convexshape, wherein the bulbous region maximum thickness is greater than aminimum thickness across the width of said abluminal surface with thedifference ranging from 3 micrometers to 100 micrometers, preferably 5micrometers to 30 micrometers. The bulbous surface region coupling theabluminal and luminal surface regions may in some instances have a flatportion at about the middle of the bulbous or convex shape.

In some examples, wherein the stent prosthesis is treated to form theregion having a bulbous shape, the bulbous region protrudes outwardlyforming a convex shape.

A concave abluminal surface region minimizes or at least reduces thepossibility of slippage of the stent when expanded to a deployedconfiguration, such that the structural elements hug the vessel wall orthe plaque area better.

In some embodiments, the stent prosthesis is formed from a substantiallycontinuous tubular body using extrusion, spraying, dipping, molding, orprinting; said tubular body has been formed into a stent comprising apattern of structural elements being radially expandable from a crimpedconfiguration to an expanded larger configuration and have sufficientstrength in the deployed configuration to support a body lumen; wherein,in cross section, surface regions extending between an abluminal surfaceregion and a luminal surface region of at least some of said structuralelements are bulbous; optionally wherein the thickness between theabluminal and luminal surfaces changes across the width of saidabluminal surface regions wherein the thickest point is substantiallytowards the sides of said structural elements wherein the difference inthickness between said thickest point and thinnest point ranges between1 micrometer and 15 micrometer, preferably between 2 micrometer and 10micrometer, more preferably between 3 micrometer and 7 micrometer;wherein the stent structural elements are coated with a coatingcomprising a drug wherein the coating contours to said structuralelements surface regions shapes wherein the thickness difference betweenthe thickest point and the thinnest point across the width of saidstructural elements ranges between 1 micrometer and 15 micrometer,preferably ranges between 2 micrometer and 10 micrometer, morepreferably ranges between 3 micrometer and 7 micrometer.

In some examples, in cross section, side surface regions of at leastsome structural elements extend outwardly forming a bulbous or convexregion; wherein said convex region has a widest point and a narrowestpoint across the thickness of said structural elements and wherein thewidest point is substantially about the center of said structuralelements side surface regions, wherein the narrowest point issubstantially about the ends of said structural elements side surfaceregion, wherein the difference between the widest and narrowest pointranges between 4 micrometer and 30 micrometer, preferably ranges between5 micrometer and 20 micrometer, most preferably ranges between 6micrometer and 15 micrometer. Optionally, the abluminal surface regioncross section is concave in shape with the difference between thickestand thinnest points of the structural element across the width of saidabluminal surface region ranges between 1 micrometer and 10 micrometers.The thinnest point across the width is generally about at the center ofthe structural element.

In some examples, in cross section, at least some structural elementshave a bulbous surface region extending between an abluminal surfaceregion and a luminal surface region wherein the bulbous surface regioncomprises portions of the luminal and abluminal surface regions and sideregions, wherein the bulbous surface regions forms variable thicknessesand widths across the thickness and widths of said structural elements;wherein said structural elements are coated with a coating comprising adrug and a polymer, wherein said coating contours to the shape of saidsurface regions maintaining a difference in thickness and widths acrossthe thickness and widths of said structural elements cross sections.

In some examples, the abluminal surface of at least some structuralelements may, in cross section, have a substantially concave shapeacross the width of the structural element, wherein the concave shape isformed between two bulbous surface regions.

In some examples, the stent prosthesis structural elements may have acoating comprising a mixture of drug and polymer, said coating beingcoated onto said structural elements wherein said coating contours tothe shape of said structural elements abluminal, luminal, and sidesurfaces.

In some examples, the stent prosthesis structural elements may have acoating comprising a mixture of drug and polymer, said coating beingcoated onto said structural elements wherein said coating contours tothe shape of said structural elements which have a substantially concaveabluminal surface shape, a substantially concave luminal surface shape,and convex side surface shapes; said coating substantially maintainingor conforming to said concave abluminal surface shape, concave luminalsurface shape, and convex side surface shapes.

In some examples, the coating may comprise a drug wherein the total drugdose ranges between 50 micrograms and 200 micrograms for an 18 mm stentprosthesis. In some examples the coating may comprise a drug wherein thetotal drug dose ranges between 2 micrograms per mm and 25 micrograms permm.

In some examples, at least some abluminal surface regions have a lip oran edge across the abluminal surface region, wherein said lip or edgehas a thickness that is different from the adjacent abluminal surfaceregion, for example wherein the difference in thickness ranges between 2micrometer and 10 micrometer.

In some examples, at least some structural elements abluminal surfacesare concave across the width of said abluminal surfaces extending alongthe length of said structural element.

In some examples at least some structural elements side surfaces areconvex across the thickness of said side surfaces extending along thelength of said side surfaces.

In some examples, at least some structural elements have concaveabluminal surface, bulbous, dogbone, or convex side surface and a lipformed along the length of said structural element. In some examples,the concave luminal and/or abluminal surface regions join convex sidesurface regions at one or more lips which extend along the side orlength of at least some of the structural elements. For example, thelips may extend continuously along a strut and a connected crown of theexpandable stent prosthesis.

In some examples, the abluminal surface region has a convex shape acrossthe width of said abluminal surface, while the luminal surface regionhas a convex, concave or substantially flat shape. In some examples bothluminal and abluminal surface regions of said structural elements aresubstantially flat. In some examples both abluminal and luminal surfaceregions are convex wherein said structural element thickest point isabout a midpoint across the abluminal and luminal surface regions, orwherein the structural element thickest point is about a midpoint acrossthe width of said structural element. In some examples of any of theprevious examples the side surface region extending between luminal andabluminal surface regions is convex.

In one example, the cross section of at least some of the stentstructural elements such as struts and/or crowns have a maximumthickness at the middle of said strut and/or crown width, or have amaximum thickness near the middle of said strut and/or crown width, orhave a maximum thickness about the middle of said strut and/or crownwidth, or have a maximum thickness between 0 to 25 micrometer offsetfrom the middle of said strut and/or crown width, or have a maximumthickness between 1% and 15% of the middle of said strut and/or crownwidth. In another example, the middle of said strut and/or crown is themidpoint of said strut and/or crown width, or is the center of saidstrut and/or crown width, or is the mid-section of said strut and/orcrown width. In some instances, the abluminal surface region of thestruts and/or crowns forms a relatively uniform curved convex surface.In some instances of the struts and/or crown cross section there is oneor more thickest points near the middle of the strut and/or crown width,that is, there is an indentation around the middle of the strut and/orcrown with the two thickest regions of the structural element flankingeach side of the indentation. The indentation may be at about the middleof the abluminal surface region or is offset from the middle in onedirection or another. In some cases, the abluminal surface region is aconvex curve with two bumps or additional convex curves along the top ofthe convex curve of the abluminal surface with a depression orindentation between the two bumps which bumps or raised sections formthe thickest regions of the struts and/or crowns. These bumps may besymmetrical or non-symmetrical in both curvature and size or thickness.In one example, the cross section of at least some of the stentstructural elements such as struts and/or crowns have a maximumthickness at about the middle of said strut and/or crown abluminalsurface width. There may, in some instances, be a lip, ledge, or a ribextending along the side surface region of the struts and/or crownslocated at about where the side surface regions meet the luminal surfaceregions and/or abluminal surface regions of the struts and/or crowns.

In a preferred example, the luminal surface of said strut and/or crownsis flat/straight, substantially flat/straight, concave, or substantiallyconcave, across the width of said strut and/or crown. In one preferredexample, the side surfaces extending between the abluminal and luminalsurfaces are convex or substantially convex. In another example, theside surface extending between the luminal and abluminal surfaces areflat or substantially flat. In one preferred example, the luminalsurface of said strut and/or crowns is substantially flat or concaveacross the width of said strut and/or crown, the side surfaces are flator convex and the abluminal surface is convex so the thickest part ofthe struts and/or crowns falls at about the middle of the width of thestruts and/or crowns. In one preferred example, the luminal surface ofsaid strut and/or crowns is substantially flat across the width of saidstrut and/or crown, the side surfaces are convex and the abluminalsurface is convex so the thickest part of the struts and/or crowns fallsat about the middle of the width of the struts and/or crowns. In anotherpreferred example, the luminal surface of said struts and/or crowns issubstantially flat or substantially concave across the width of saidstrut and/or crown, the side surfaces are flat or convex and theabluminal surface is convex with an indentation at about the middle ofthe width of the abluminal surface region. In another preferred example,the luminal surface of said struts and/or crowns is substantially flatacross the width of said strut and/or crown, the side surfaces areconvex and the abluminal surface is convex with an indentation at aboutthe middle of the width of the abluminal surface region.

In one example, the cross section of at least some of the stentstructural elements, such as struts and/or crowns, has a maximumthickness at about the middle of said strut and/or crown width; themaximum thickness is located adjacent to a depression or indentation atabout the middle of the strut and/or crown abluminal surface; or themaximum thickness is located adjacent to a depression or indentation atabout the middle of said strut and/or crown width. In a preferredexample, the luminal surface of said strut and/or crowns isflat/straight, substantially flat/straight, concave, or substantiallyconcave, across the width of said strut and/or crown. In a preferredexample, the side surfaces extending between the abluminal and luminalsurfaces are convex or substantially convex. In another example the sidesurface extending between the luminal and abluminal surfaces are flat orsubstantially flat. In some examples, the side surface regions slantslightly outward between the side surface region and luminal surfaceregion so the width at a region adjacent to the luminal surface isgreater than the width of the struts and/or crowns at a region adjacentto the abluminal surface region.

In another example, the cross section of said struts and/or crownsabluminal surface has a depression or indentation at about themid-section (or about the middle or about a mid-point) of said strutand/or crown abluminal surface. In a preferred example, the luminalsurface of said strut and/or crowns is flat/straight, substantiallyflat/straight, concave, or substantially concave across the width ofsaid strut and/or crown. The depression or indentation at about themid-section of the said strut on the abluminal surface provides forincreased interaction of the artery vessel wall with the strut as thestent is deloyed from a crimped configuration to the deployedconfiguration in a body lumen. The depression or indentation about themid-section of the said strut on the abluminal surface provides forreduced scaffold slippage, and improved scaffold placement duringimplantation of the scaffold in a body lumen.

In a preferred example the luminal surface of said strut and/or crownsis flat/straight, substantially flat/straight, concave, or substantiallyconcave, across the width of said strut and/or crown. Such luminalsurface shapes provide a smaller strut thickness, lower crimp profile,better fit onto the delivery system, reduced blood flow disturbance inthe artery, or better or faster endothelialization of the implantedstent. The substantially flat or substantially concave luminal surfacemay be combined with any of the described abuminal and side surfaceregions, including for example, concave or convex abluminal surfaceregions and flat or convex side surface regions.

In one example, the thickness of the indentation or depression on theabluminal surface region ranges between 1 micrometer and 50 micrometer,preferably ranges between 1 micrometer and 25 micrometer, and mostpreferably ranges between 1 micrometer and 15 micrometer. In oneexample, the width of said depression or indentation at or near thewidest point or section of the depression or indentation ranges between1 micrometer and 50 micrometer, preferably ranges between 1 micrometerand 25 micrometer, and most preferably ranges between 1 micrometer and15 micrometer. While the depression or indentation is depicted in thedrawings as a concave depression in the otherwise convex abluminalsurface region of the struts and/or crowns, the indentation ordepression can have any shape such as concave, square, rectangle, Ushape, etc. In some examples, the indentation or concave section of theconvex abluminal surface does not extend across the width of theabluminal surface region and only extends about one fourth of thedistance between the side surface regions.

In another example, the cross section of said struts and/or crowns hasan abluminal surface that is substantially convex across the width ofsaid struts and/or crowns. In another example said struts and/or crownshave a substantially convex shape abluminal surface and have sidesurfaces that are substantially straight or convex. In another examplethe cross section of said struts and/or crown abluminal surface issubstantially convex across the width of said strut and/or crown and theabluminal surface has an indentation or depression at about the middlepoint of said strut and/or crown abluminal surface. In another example,the cross section of said struts and/or crown has an abluminal surfacethat is substantially convex across the width of said strut and/or crownand the abluminal surface has an indentation or depression about 1micrometer to about 25 micrometer from the middle point of said strutand/or crown abluminal surface.

In another example the cross section of said struts and/or crowns has anabluminal surface that is substantially convex across the width of saidstrut and/or crown and has the maximum thickness about the middle ofsaid width. In another example of any of the previous examples the crosssection of said struts and/or crown having an abluminal surface that issubstantially convex across said abluminal surface of said strut and/orcrown and the abluminal surface has an indentation or depression atabout the middle point of said abluminal surface with the maximumthickness of said strut and/or crown located adjacent to saidindentation or depression.

It can be appreciated that all these examples within this applicationare applicable to all biodegradable materials including polymeric andmetallic materials. It can also be appreciated that all the examples offorming with desired shape and treating to form a desired shape areapplicable to all biodegradable materials including polymeric andmetallic materials.

In some examples, the stent prosthesis is formed as a tubular body byextrusion, dipping, molding or printing and then patterned into a stent.In some examples the stent prosthesis is formed as a sheet, wherein thesheet is rolled to form a tubular body wherein the sheet is patternedinto a stent before or after forming into a tubular body. The rolledsheet edges are affixed or joined together to form a tubular body bytreatment such as using heating, chemical bonding, ultrasound bonding,laser bonding or other means. In some examples the stent prosthesis isformed as a sheet, wherein the sheet is patterned prior to rolling thepatterned stent into a tubular patterned stent using the methodsdescribed previously. In some examples, the stent prosthesis is formedas a tubular pattered body, wherein the patterning and forming of thetubular body take place concurrently, such as the example of 3-Dprinting. In some examples, the stent prosthesis is formed as a threedimensional structure or body and then patterned into a stent. In someexamples, the stent prosthesis is formed as a substantially tubular bodyand then patterned into a stent. In any of the above examples thestructural elements are formed with the desired shape or treated to formthe desired shape as described herein.

In a preferred example, the luminal surface of said strut and/or crownsof any of the examples is flat/straight, substantially flat/straight,concave, or substantially concave, across the width of said strut and/orcrown.

In a preferred example, the biodegradable stent is heat treated one ormore times after patterning and before crimping. Heat treating thebiodegradable stent after patterning and before crimping provides for atleast some of the following: increased radial strength in the deployedconfiguration. aligning the polymeric material orientation in the radialdirection, increase orientation of the polymeric material in the radialdirection, and reduced residual solvent in the stent. In one example,heat treating the biodegradable stent after patterning and aftertreatment to form the desired shape cross sectional shape for the strutsand/or crowns and before crimping provides for substantially maintainingthe stent pattern.

It can be appreciated that a prosthesis may have any or all of thefeatures set out in this document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example of a two dimensional stent pattern;

FIGS. 2A-2C are SEM images taken at a magnification of 1000-1200×showing a cross section of a stent structural element, in these images,showing a bulbous region extending between the abluminal surface regionand the luminal surface region;

FIG. 3 is a cross section of a stent structural element having a concaveabluminal surface region, a concave luminal surface region, and twoconvex side surface regions, showing a bulbous region extending betweenthe luminal surface region and abluminal surface region;

FIG. 4 is a cross section of a stent structural element having convexside surface regions, a concave abluminal surface region and asubstantially straight/flat luminal surface region, showing a bulbousregion extending between the abluminal surface region and the luminalsurface region;

FIG. 5 is a cross section of a stent structural element having twoconvex side surface regions, a substantially straight/flat abluminalsurface region and a concave luminal surface region, showing a bulbousregion extending between the abluminal surface region and the luminalsurface region;

FIG. 6 is a cross section of a stent structural element havingsubstantially straight side surface regions, a concave abluminal surfaceregion and a concave luminal surface region, showing a bulbous region inthe abluminal surface region extending or protruding outwardly and abulbous region in the luminal surface region extending or protrudingoutwardly;

FIG. 7 is a cross section of a stent structural element having convexside surface regions, a concave abluminal surface region and a concaveluminal surface region with a center part of the concave surface regionsbeing substantially straight (flat), showing a bulbous region extendingbetween the abluminal and luminal surface regions extending outwardly;

FIG. 8 is a cross section of a stent structural element having concaveside surface regions, a concave abluminal surface region and a concaveluminal surface region, showing bulbous regions in the abluminal surfaceregion extending or protruding outwardly and bulbous regions in theluminal surface region extending or protruding outwardly;

FIG. 9 is a cross section of a stent structural element having a dogboneshape comprising concave luminal and abluminal surface regions, andconvex side surface regions, showing a bulbous region extending betweenthe abluminal surface region and the luminal surface region where thebulbous region comprises an abluminal surface region that has a convexshape towards the end of the structural element width and a luminalsurface region that has a convex shape towards the end of the structuralelement width;

FIG. 10 is a cross section of a stent structural element having aracetrack shape with substantially flat luminal and abluminal surfaceregions, and convex side surface regions;

FIG. 11 is a cross section of a stent structural element having anelliptical shape with convex luminal and abluminal surface regions, andconvex side surface regions;

FIG. 12 is a schematic illustration of the difference in tensile andcompressive stress distribution between a treated and untreated stents;

FIG. 13 is a schematic cross section of a balloon showing a pair ofstruts having modified/treated surface regions and a pair of strutshaving unmodified surface regions;

FIG. 14 is a cross section of a crimped stent having unmodified sidesurface regions;

FIG. 15 is a cross section of a crimped stent having modified sidesurface regions;

FIG. 16 is a graph of the results of trackability testing;

FIG. 17 is a schematic illustration of a laser process for creatingconvex side surface regions;

FIG. 18 is a schematic illustration of a laser process for creatingconcave luminal or abluminal surface regions;

FIG. 19 is a perspective view showing an example of a stent prosthesisshowing the stent pattern;

FIG. 20 is a two dimensional top view showing an example of a part of astent prosthesis, showing the stent pattern;

FIG. 21 is a side perspective view showing an example of a stentprosthesis showing the stent pattern;

FIG. 22 is an example of a stent structural element, for example astrut, cross section before treatment;

FIG. 23 is an SEM image at 1000× magnification showing a cross sectionof a further stent structural element showing concave a abluminalsurface and convex side surfaces, wherein the region extending betweenthe abluminal and luminal surfaces is bulbous, or dogbone, wherein thestructural element shows variable thickness and variable width;

FIG. 24 is an SEM image at 500× magnification showing an abluminalperspective view of a stent structural element such as a strut, a crownor a link showing a lip extending along the strut and crown; and

FIG. 25 is a cross section of a stent structural element such as a struta crown, or a link which has been treated and viewed using Micro-Vu atapproximately 315× magnification.

FIG. 26 is an example of an SEM image at about 1000× and about 250×magnification showing maximum thickness about middle of strut crosssection, convex abluminal surface region.

FIG. 27 is an example of an SEM image at about 1000× and about 250×magnification showing maximum thickness near middle and an indentationadjacent to thickest section of the abluminal surface region.

FIG. 28 is an example of an SEM image at about 1000× and about 250×magnification showing maximum thickness near middle of the abluminalsurface region of the strut cross section and convex sides.

FIG. 29 is an example that shows a strut cross section with maximumthickness of 0.118 mm near the middle of the abluminal surface region ofthe strut cross section, with radiused edges adjacent to the abluminalsurface of 0.066 mm, substantially convex sides, and a luminal surfacethat is concave.

FIG. 30 is an example that shows a strut cross section with maximumthickness of 0.110 mm, a concave surface near the middle of theabluminal surface region of the strut cross section 0.005 mm deep, withradiused edges adjacent to the abluminal surface of 0.050 mm,substantially convex sides, and a luminal surface that is concave.

FIG. 31 is an example that shows a cross section of a strut having amaximum thickness about the middle of the abluminal surface of the strutand/or crown, with a concave luminal surface.

FIG. 32 is an example that shows a cross section of a strut having amaximum thickness at the middle of the abluminal surface region of thestrut and/or crown with a substantially flat luminal surface.

FIG. 33 is an example that shows a cross section of at least some of thestent structural elements such as struts and/or crowns having a maximumthickness about the middle of the abluminal surface region of the strutand/or crown, the maximum thickness located adjacent to a depression orindentation about the middle of the strut and/or crown abluminalsurface, with a concave luminal surface.

FIG. 34 is an example that shows a cross section of at least some of thestent structural elements such as struts and/or crowns having a maximumthickness about the middle of the strut and/or crown width, the maximumthickness located adjacent to a depression or indentation about themiddle of the strut and/or crown abluminal surface, with a flat luminalsurface.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments provide an expandable biodegradable stent prosthesiscomprising: a tubular expandable stent prosthesis body comprising abiodegradable material, for example a polymeric biodegradable material,said expandable stent prosthesis body comprising stent structuralelements each having a luminal surface and an abluminal surface and athickness between said luminal and abluminal surfaces; wherein a regionextending between the abluminal surface and the luminal surface of atleast some structural elements is bulbous.

Embodiments provide an expandable biodegradable stent prosthesiscomprising: a tubular expandable stent prosthesis body comprising abiodegradable material, for example a polymeric biodegradable material,said expandable stent prosthesis body comprising stent structuralelements each having a surface with a luminal surface region, anabluminal surface region, coupling portions coupling the abluminal andluminal surface regions, and a thickness between said luminal andabluminal surface regions; wherein at least a part of at least some ofthe coupling portions is bulbous.

Embodiments provide an expandable biodegradable stent prosthesiscomprising: a tubular expandable stent prosthesis body comprising abiodegradable material, for example a polymeric biodegradable material,said expandable stent prosthesis body comprising stent structuralelements each having an interior, luminal, surface region and anexterior, abluminal, surface region such that when the stent prosthesisis placed in the lumen of a vessel, the luminal surface regions face thelumen of the vessel and the abluminal surface regions face the vesselwall; wherein at least some of the abluminal surface regions have aconcave shape across substantially the width of said surface regions;and/or at least some of the luminal surface regions have a concave shapeacross substantially the width of said surface regions; and/or at leastsome of the side surface regions coupling the abluminal and luminalsurface regions have a straight, convex or concave shape acrosssubstantially the width of said surface regions.

In a preferred example, the luminal surface of said strut and/or crownsis flat/straight, substantially flat/straight, concave, or substantiallyconcave, across the width of said strut and/or crown. In one preferredexample, the side surfaces extending between the abluminal and luminalsurfaces are convex or substantially convex. In another example, theside surface extending between the luminal and abluminal surfaces areflat or substantially flat. In one preferred example, the luminalsurface of said strut and/or crowns is substantially flat or concaveacross the width of said strut and/or crown, the side surfaces are flator convex and the abluminal surface is convex so the thickest part ofthe struts and/or crowns falls at about the middle of the width of thestruts and/or crowns. In one preferred example, the luminal surface ofsaid strut and/or crowns is substantially flat across the width of saidstrut and/or crown, the side surfaces are convex and the abluminalsurface is convex so the thickest part of the struts and/or crowns fallsat about the middle of the width of the struts and/or crowns. In anotherpreferred example, the luminal surface of said struts and/or crowns issubstantially flat or substantially concave across the width of saidstrut and/or crown, the side surfaces are flat or convex and theabluminal surface is convex with an indentation at about the middle ofthe width of the abluminal surface region. In another preferred example,the luminal surface of said struts and/or crowns is substantially flatacross the width of said strut and/or crown, the side surfaces areconvex and the abluminal surface is convex with an indentation at aboutthe middle of the width of the abluminal surface region.

Each stent structural element (for example struts or other stentstructures such as crowns or links) has a particular (certain) surfaceregion geometry or is modified according to a treatment processdescribed herein to provide that certain geometry. As an example, anexpandable stent prosthesis may be formed by laser patterning or cuttingfrom a tube or sheet of polymeric material to provide stent structuralelements (for example struts or other stent structures such as crowns),with many having substantially rectangular or square cross sections andthe expandable stent prosthesis may be treated to provide the certaingeometry such as convex side surface regions and/or concave or flatabluminal surface regions.

An exemplary stent pattern is shown in FIG. 1 represented in twodimensions. The stent body 200 comprises stent structural elementsforming sinusoidal rings, in this example the stent structural elementscomprise struts 210 and V or U shaped crowns 230 joining the struts. Therings are interconnected by links 220. In the example stent patternshown, links 220 connect adjacent crowns. A length of the stent can beadjusted by changing a number of rings. Some of the links 220 or struts210 may be replaced by or attached to one or more loops 224 eachcontaining one, two or more radiopaque markers axially or radially orsomewhere in between. For example two such pairs of radiopaque markerscan be provided at the opposite ends of the stent, and/or at theopposite side of the stent. The stent 200 can be balloon expandable andhas low recoil, has sufficient radial strength to support a body lumen,conformable to the body lumen, and has low percent shortening uponexpansion of less than 15%. Many other stent structures includediffering arrangements of struts, crowns, links and other structureswhich together form a balloon expandable stent, or stent body, and canbe modified according to the methods described herein. The stent canalso be self-expandable, or self-expandable prior to balloon expansion,or can self-expand to a second larger diameter than a first deployeddiameter after recoil from said first deployed diameter. The stentstructures (e.g. struts) have luminal and abluminal surface regions andtwo side surface regions extending between the luminal and abluminalsurface regions as can be seen in the cross sectional views of FIGS.2-11. Stent structural elements, may have a thickness of 100 micrometer,but the thickness can range from 25 micrometer to 500 micrometer, orfrom 75 micrometer to 300 micrometer, or preferably from 100-200micrometers. The strut length (the longest dimension) may be 0.75 mm,but strut length can range from 0.35 mm to 3 mm, preferably from 0.5 mmto 1.5 mm, or other. The width of stent structural elements may be 150micrometer, but can range from 50 to 500 micrometer, from 100 to 300micrometers or from 150 to 250 micrometers.

Other embodiments of stent and materials and treatments therefore aredescribed in further detail in U.S. Pat. Nos. 8,182,890; 8,323,760;8,636,792; 8,814,930; and U.S. Patent Publication Nos. 2008/0177373 and2006/0029711 which have been previously incorporated by referenceherein.

An exemplary patterned stent 170 is shown in FIG. 19. The patternedstent, stent or stent body 170 has struts 174 joined by crowns 172. Thepatterned stent has luminal surface regions 176 facing the lumen of theblood vessel, and abluminal surface regions 178 which face the bloodvessel wall or faces the lumen wall. Each of the stent structures suchas struts, crowns, and links, has two side surface regions extendingbetween the luminal and abluminal surface regions. The rings 173 eachcomprise struts 174 joined by crowns 172. The rings 173 can be in-phaseor out-of-phase or a combination thereof and are interconnected by links175. A ring 173 is connected to an adjacent ring by links 175, or alsosome adjacent crowns are connected by links 175. Some of the links 175may be attached to or replaced by one or more loops each containing one,two or more axially or radially displaced radiopaque markers, orradiopaque markers may be placed in the end rings of the patternedstent. The patterned stent 170 is balloon expandable and has low recoil,sufficient radial strength to support a body lumen or blood vessel,conformability to the body lumen or blood vessel, and low percentshortening upon expansion of less than 15%.

Many other stent patterns including differing arrangements of struts,crowns, links and other structures which together form a balloonexpandable structure are possible. Two such examples are shown in FIGS.20 and 21.

FIG. 20 depicts a two dimensional view of a part/portion of a patternedstent 180 having a plurality of struts 182 joined by crowns 184. Asshown in FIG. 20, the crowns 184 are connected by U-shaped links 186which alternate in directions (upward and downward directed) dependingon axial location along the length of the stent. The U-shaped links 186may be replaced with straight, S-shaped, W-shaped or other shaped linksand may be positioned at every crown or at some crowns, every othercrown, or other numbers of crowns. In addition to links connectingadjacent rings, typically connecting adjacent crowns of adjacent rings,links can also connect/interconnect struts to other struts or crowns ofadjacent rings. In addition to or as an alternative to rings, orserpentine ring patterns, helically wound rings, or helically woundserpentine patterns can also be used.

FIG. 21 depicts an example of a patterned stent 190 having struts 192and crowns 194 joining struts. Optionally as seen in the patterned stentof FIG. 21, link 196 connects two adjacent crowns. The links 196 may bestraight, sinusoidal, or other shaped. One, two or more links 196 canconnect the stent rings. The struts shown in the stent examples of FIGS.1 and 19-21 are straight; however some or all of these straight strutscan be replaced by curved or other shaped struts. Struts can be axiallyaligned in a crimped configuration or can be at an angle to thelongitudinal axis. Upon expansion of the stent, generally the anglebetween the struts and the longitudinal axis of the stent increases.

In a stent pattern, generally crowns join struts, for example crowns mayjoin two struts or three or four struts, or other. Crowns can bestraight, arc, semi-circular, or key hole shaped, or other crown shapesthat connect struts. Struts can be straight, wavy, or other strutshapes. Struts may extend axially, in a helical direction, or otherdirection such as between an axial direction and a radial direction.Crowns can be connected to adjacent crowns. Crowns may be connected toadjacent crowns by a link, such link can be straight links, or haveother shapes such as U, V, W, S, or other shapes or geometries. Crownsconnected to adjacent crowns by links typically connected on any pointsor areas along the length of the crown may be connected to adjacentcrowns without a link, at the point of intersection of the adjacentcrowns or at any other point along the length of the adjacent crownswhere they meet. Crowns may be connected to adjacent crowns by fusingthe two crowns into one, such as in the embodiment of FIG. 21.

The terms “scaffold structures,” “stent structures,” and “stentelements” as used herein comprise stent structural elements such asstruts, links, crowns, elements or other structural components of thestent prosthesis. Together these stent structural elements form a stent,scaffold, stent body, prosthesis, or prosthesis body. The terms“scaffold, “stent”, and “prosthesis” can be used interchangeably.

The term “bulbous” or as used herein means resembling a bulb in shape,curving outwardly in a convex shape, protruding, protruding outwardly,extending, extending outwardly, bulging, bulb like, bulb shape,swelling, outwardly protruding or extending in a convex shape. A“dogbone” shape has opposed bulbous ends which need not necessarily beof the same size, shape or be uniform or symmetrical.

The term “concave” as used herein means hollowed or rounded inward likethe inside of a bowl, sphere, circle, or other geometric shape such asan ellipse or parabola, arched in or curving in, and also may include astepped series of surface regions which together form a concave shape.

The term “convex” as used herein means curved outward the exterior of abowl sphere, circle or other geometric shape such as an ellipse orparabola, arched out or curving out, and also may include a steppedseries of surface regions which together form a convex shape.

The surface region that has a concave or convex shape may be a smoothlycontinuous surface region, a surface region that has a concave or convexshape may have one or more discontinuities, depressions, protrusions orother perturbations, provided that the overall shape or form of thesurface region is concave or convex shape. The bulbous surface regionsmay in some instances have one or more discontinuities, depressions,protrusions or other perturbations, provided that the overall shape orform is bulbous.

In disclosed embodiments, surface regions of stent structural elementscreated during laser cutting are modified to provide a shape whichimproves mechanical performance of the stent and/or provides improveddrug delivery from the stent or from a coating on the shaped stent. Themodified surface regions formed by the methods described herein mayoccur on some or substantially all stent structural elements.

The flat side surface regions extending between the luminal andabluminal surface regions of the stent structural elements (e.g. struts,crowns, links and/or other structures) of the stent created by afabrication process such as laser cutting can be modified to form convexside surface regions, preferably convex side surface regionssubstantially along the thickness of the stent structural element. Theconvex side surface regions in either the convex or bulbous shapefunction to more widely distribute tensile stresses and compressivestresses along the stent and can increase radial strength of the stent.The dimension of a stent structural element between the luminal andabluminal surface regions is the thickness of the stent structuralelement. In some instances, the convex or bulbous shape of the sidesurface regions joining the abluminal and luminal surface regions mayhave a flat portion in about the middle of the side surface between theabluminal and luminal surface regions.

The flat or slightly convex abluminal surface regions of the stentstructural elements can be modified by the processes/treatment describedherein to form concave or flat abluminal surface regions. The flat orslightly concave luminal surface regions of the stent structuralelements can be modified by the processes/treatment described herein toform concave luminal surface regions. In some instances, the concaveshape of the abluminal surface region may have a flat portion at aboutthe middle of the abluminal surface region or at about the middle of thewidth between the two side surface regions. Concave abluminal surfaceregions can provide benefits in drug coating and in drug delivery andbenefits of embedding the stent into the vessel wall and convex sidesurface regions can provide benefits in retaining the stent on a ballooncatheter, and also improved trackability in tortuous anatomy. Convexside surface regions make it easier to insert the stent on the catheterinto and through the blood vessel to the desired location. The dimensionof a stent structural element between its side surface regions is thewidth of the stent structure. The concave curvature of the abluminaland/or luminal surface regions extends substantially across the width ofthese surface regions.

The stent prosthesis may be further coated with a coating comprising atleast one drug and at least one polymer, wherein the coating follows thecontour of the underlying surface region, in a preferred embodiment,without substantially changing the luminal, abluminal or side surfaceregion shapes.

The luminal and abluminal surface regions of the stent structuralelements can be fabricated or modified by the processes described hereinto form substantially dumbbell, barbell, bow tie, or dogbone shapedstent structural elements or cross section stent structural elements.

FIGS. 2A-2C are SEM images showing cross sections of stent structuralelements which have been modified to have a shape designed for improvedstent performance. The stent structural elements of each of FIGS. 2A-2Chave a luminal surface region (bottom), an abluminal surface region(top), and two side surface regions. As shown in FIGS. 2A-C, theabluminal surface region is substantially concave across the width ofthe abluminal surface region while the two side surface regions aresubstantially convex across the thickness of the side surface regions ofthe strut. These structural elements cross sections of convex and/orconcave surface regions form the dogbone, dumbbell, barbell or bulbousshape. This fabricated shape or modified/treated shape can distributetensile stresses and compressive stresses along of the stent and canprovide improved radial strength of the stent. The SEM images of FIGS.2A-C are taken at a magnification of 1200× to show the stent structuralelement features at the micrometer level.

FIG. 22 shows an example of a cross section of a stent structuralelement before modification or treatment when the strut is a part of astent formed from a tube. The abluminal surface region 252 of theuntreated stent structural element is slightly convex due to the overallcurvature of the tube. Similarly, the luminal surface region 254 isslightly concave due to the curvature of the tube. The side surfaceregions 250 extend from the abluminal to the luminal surface regions andmay be parallel or non-parallel depending on the process used to formthe tubular stent but are generally flat/straight.

In embodiments, the modification of the stent surface region shapesimproves tracking (maneuverability) and/or push by reducing the forcerequired to track or push the stent mounted on a catheter through acylindrical body, such as a blood vessel. The reduction of track or pushforce is achieved because of the changing of the area of surface regioncontact between the modified stent shape and the vessel. On theabluminal side, the unmodified surface regions on the stent structurecan act like ratchet elements as the stent is pushed through a bloodvessel, especially one with calcified lesions. This may hinder trackingor movement through the vessel because the unmodified side regions canget caught on the walls of the vessel. On the luminal side, theunmodified side regions of the stent can inhibit a guidewire or catheterfrom going through one of the spaces between stent structures, such asfor treatment of a bifurcation. In order to improve tracking or passageof guidewire and catheter, it is beneficial to modify the shapes of thesurface regions on the stent structure. The modification of the shape ofthe surface regions to provide convex surface regions, concave surfaceregions or a combination thereof improves performance of the stent.

Examples of processes which can be used to shape the surface regions ofthe stent structures include solvent treatment, media blasting, abrasivetumbling, mechanical shaping, laser shaping, heat treatment or othershaping processes. The processes of shaping the surface regions of thestent create substantially convex side surface regions extending fromthe luminal to the abluminal edge. The convex side surface regions canhave radii of curvatures of about 0.020 to about 0.375 mm, about 0.030to about 0.200 mm, or about 0.050 to about 0.175 mm. The processes ofshaping the surface regions of the stent can also create substantiallyconcave abluminal surface regions extending between the side surfaceregions. The concave luminal and/or abluminal surface regions can haveradii of curvatures of about 0.020 to about 0.500 mm, about 0.030 toabout 0.200 mm, or about 0.050 to about 0.175 mm. The concavity of theabluminal surface regions may extend substantially across the width fromone side surface region of the stent structure to the other side surfaceregion of the same structure, with a single concave depression, or aconcave shape. Similarly, the convexity of side surface regions of thestent structures may extend across the thickness substantially from theluminal to the abluminal surface region of the same structure as oneconvex surface region, or as a convex shape.

The stent structures can be shaped before and/or after the applicationof a polymer/drug coating layer to the exterior of the stent. The shapetreatment may be performed on the stent structure followed by coatingwith drug matrix coating wherein the coating process does notsubstantially change the shape of the surface regions but conforms tothe concave and convex shapes of the treated surface regions.

The concave luminal surface regions after the treatment process may havea concave shape with a radius of curvature different than the radius ofcurvature of the inner diameter of the tube from which the stent isformed.

The ratio of radius of curvature of at least a portion of the luminal orabluminal surface region of the stent structure to the radius ofcurvature of the side of the stent structure may be less than one.

The ratio of radius of curvature of at least a portion of the luminal orabluminal surface region of the stent structure to the radius ofcurvature of the side of the stent structure may as another possibilitybe greater than one.

As another possibility, the radius of curvature of at least a portion ofthe luminal or abluminal surface region of the stent structure may besubstantially equal to the radius of curvature of the side of the stentstructure.

The radius of curvature of at least a portion of the concave luminal orabluminal surface regions may be greater than the radius of curvature ofat least a portion of the convex side surface regions.

The cross section of a stent structure (stent structural element), mayform a substantially dumbbell, barbell, bow tie, scalloped or dogboneshaped cross section structure.

Examples of shaped cross sections of stent structures are shown in FIGS.3-11 each having a surface with a luminal surface region, an abluminalsurface region, coupling portions coupling the abluminal and luminalsurface regions, and a thickness between said luminal and abluminalsurface regions; wherein at least a part of at least some of thecoupling portions is bulbous. These stent structures can represent anystent structure including struts, crowns or/and links. The stentstructure cross section shown in FIG. 3 includes a concave abluminalsurface region 32 and a concave luminal surface region 34 and two convexside surface regions 30 extending between the luminal and abluminalsurface regions of the stent structure. The convex shape of the sidesurface regions 30 extends substantially across the thickness of thestent structure to provide two bulbous regions. The concave shape of theabluminal and luminal surface regions 34, 32 extends substantiallyacross the width of the stent structure. FIGS. 29-34 show struts withconvex abluminal surface regions, flat or convex side surface regionsand concave or substantially flat luminal surface regions.

The stent structure cross section shown in FIG. 4 includes two convexside surface regions 40, as well as a concave abluminal surface region42 and a substantially flat luminal surface region 44 so that bulbouscoupling portions are provided by the abluminal surface region 42 andthe side surface regions 40. The stent structure cross section of FIG. 5includes two convex side surface regions 50, as well as a substantiallyflat abluminal surface region 52 and a concave luminal surface region 54so that bulbous coupling portions are provided by the luminal surfaceregion 54 and the side surface regions 50. The stent structure crosssection of FIG. 6 includes substantially flat side surface regions 60,as well as a concave abluminal surface region 62 and a concave luminalsurface region 64 so that bulbous coupling portions are provided by theabluminal surface region 62 and the side surface regions 60 and by theluminal surface region 64 and the side surface regions 60. The stentstructure cross section of FIG. 7 includes convex side surface regions70, as well as a concave abluminal surface region 72 and a concaveluminal surface region 74 so that bulbous coupling portions are providedby the abluminal surface region 76 and the side surface regions 70 andby the luminal surface region 74 and the side surface regions 70. Theconcave abluminal and luminal surface regions 72, 74 may include asubstantially flat center portion 76 which forms a bottom part of theconcave surface region. Similarly, the convex side surface regions 70can include flat portions. The stent structure cross section of FIG. 8includes two concave side surface regions 80, as well as a concaveabluminal surface region 82 and a concave luminal surface region 84 sothat bulbous coupling portions are provided by the abluminal surfaceregion 82 and the side surface regions 80 and by the luminal surfaceregion 84 and the side surface regions 80.

The stent structure cross section of FIG. 9 includes substantiallyconvex side surface regions 90, as well as a concave abluminal surfaceregion 92 and a concave luminal surface region 94 and roundedintersection of the concave and convex surface regions, which togetherform a dogbone shaped cross section so that bulbous coupling portionsare provided by the side surface regions 90. In the example of FIG. 9,the shape of the stent structure is such that it can embed or nest thestent into the vessel wall upon expansion providing better stentapposition to the surrounding tissue. In contrast, square or rectangularflat cross section abluminal stent structure surface regions may inhibitembedding because the substantially flat surface regions push on theuneven plaque covered vessel wall during expansion.

The stent structure cross section of FIG. 10 includes convex sidesurface regions 98, a substantially flat abluminal surface region 96 anda substantially flat luminal surface region 97.

The stent structure cross section of FIG. 11 includes convex sidesurface regions 100, a convex abluminal surface region 102 and a convexluminal surface region 104, which also is an elliptically shaped crosssection. The stent structure cross section of FIG. 29 depicts a strutwith a convex abluminal surface region, convex side surface regions anda concave luminal surface region. FIG. 30 shows a strut with a convexabluminal surface region that has a concave surface near the middle ofthe abluminal surface region of the strut cross-section, a concaveluminal surface region and convex side surface regions. FIG. 31 shows astrut with a convex abluminal surface region, convex side surfaceregions and a concave luminal surface region. FIG. 32 shows a strut witha convex abluminal surface region, convex side surface regions and asubstantially flat luminal surface region. FIG. 33 depicts a strut witha convex abluminal surface that has a concave surface or depression nearthe middle of the abluminal surface region, convex side surface regionsand a concave luminal surface region. FIG. 34 shows a strut with aconvex abluminal surface region that has a concave surface or depressionregion near the middle of the abluminal surface region, convex sidesurface regions and a substantially flat luminal surface region.

The convex and/or bulbous surface regions of the cross sections depictedin FIGS. 3-11 can distribute tensile stresses and compressive stressesalong of the stent and can provide improved radial strength of thestent. Although the cross sections of FIGS. 3-11 and 29-34 have beenshown as symmetrically shaped about a midline of the stent structure,the cross sections can also be asymmetrically shaped. The curvature ofany of the surfaces may be asymmetrical along its curve and thecurvature of the side surfaces may not be uniform one to the other. Atleast a portion of the stent structure with a concave abluminal surfaceregion may have a minimum cross sectional thickness of between 50 to 300micrometers, preferably between 75 to 200 micrometers, more preferablyfrom 100 to 150 micrometers.

At least a portion of the stent structure with a concave abluminalsurface region may have a maximum cross sectional thickness of between50 to 500 micrometers, preferably between 75 to 300 micrometers, morepreferably from 100 to 200 micrometers.

At least a portion of the stent structure with a convex side surfaceregion may have a minimum cross sectional width of between 50 to 300micrometers, preferably between 75 to 300 micrometers, more preferablyfrom 100 to 150 micrometers.

At least a portion of the stent structure with a convex side surfaceregion may have a maximum cross sectional width of between 50 to 500micrometers, preferably between 75 to 300 micrometers, more preferablyfrom 100 to 200 micrometers. Measurements described herein of thedimensions including widths, thicknesses, radii of curvature and thelike may be made on the actual prosthesis or on enlarged views of theprosthesis by SEM or microscope, such as the SEM 1200X images in FIGS.2A-C and FIGS. 23 and 24. Other means of viewing the bulbous region,convex side surface region, or concave abluminal surface region can alsobe accomplished using microscope or Micro-Vu at magnifications rangingfrom 500×-1500×. FIG. 25 is a cross section of a treated stentstructural element viewed using Micro-Vu at approximately 315×magnification with the abluminal surface on the top in the figure.

The maximum and minimum dimensions described herein may be measured on asingle structural element, strut, crown or link. In some examples themaximum or minimum dimensions may be the mean of multiple points atdifferent locations on one or more structural elements.

After the shaping process treatment, the variance in stent structuredimensions along the length of the stent may be less than 40%,preferably less than 25%, more preferably less than 10%. In someembodiments, the tubular body, stent or stent may be formed from atleast one biodegradable polymer or other biodegradable material havingdesired degradation characteristics where the polymer may be modified tohave the desired crystallinity, Tg, recoil, strength, shortening,expansion characteristics, crimping characteristics, molecular weight,and/or other characteristics. The tubular body or stent may be modifiedor treated by one or more treatments before, after or during patterningwherein the treatment comprises at least one or more of heating,cooling, pressurizing the polymeric material, chemically treating thepolymeric material, or mechanically stamping the polymeric material.

Biodegradable polymers include one or more polymers, copolymers, blends,and combination thereof of: lactides, caprolactones, and glycolides.Some examples include poly-DL-Lactide, polylactide-co-glycolactide;polylactide-co-polycaprolactone, poly (L-lactide-co-trimethylenecarbonate), polylactide-co-caprolactone, polytrimethylene carbonate,elastin, fibrin, collagen and copolymers; polyhydroxybutyrate;polyhydroxyvalerate, poly orthoesters, poly anhydrides, tyrosine derivedpolycarbonates, polyiminocarbonates, and the like. The biodegradablepolylactide based polymer may comprise a copolymer of L-lactide andglycolide, preferably with a weight ratio of 85% L-lactide to 15%glycolide. As another example the biodegradable polylactide basedpolymer may comprise a copolymer of L-lactide and caprolactone,preferably with a weight ratio of 90% L-lactide to 10% caprolactone.

In some examples, the tubular body, stent or stent comprises adegradable polymeric material wherein the polymeric material comprisesone or more polymers; or one or more co-polymers; or one or more blendsof monomers, polymers or copolymers; and combinations thereof. Thepolymeric material may comprise one or more polymer or one or moreco-polymer. Additionally, at least one monomer, polymer, or co-polymerof similar material (to the one or more polymer or the one or moreco-polymer) is blended with the polymeric material.

In some examples, a biodegradable stent comprising a polymeric materialcomprises a copolymer of lactide and caprolactone in the ratio by weightranging from 80-99% lactide to 1-20% caprolactone; wherein the polymericmaterial further comprises a monomer or polymer including a copolymer ofone or more of the following: lactide, glycolide, lactide glycolide,caprolactone, and lactide caprolactone; wherein the one or more monomeror polymer total amount is 1 to 100 micrograms per milligram ofpolymeric material, preferably 5 to 75 micrograms per milligram ofpolymeric material, more preferably 10 to 50 micrograms per milligramsof polymeric material; wherein the stent with the modified structurecross section is capable of being crimped from an expanded configurationto a smaller crimped configuration, and at body temperature capable ofbeing expanded to a deployed configuration, and having sufficientstrength when expanded to support a body lumen, without fracture of thestent.

The one or more monomer and/or polymer may change (increase or decrease)the crystallinity of the polymeric material by 5% to 150%, preferably by10% to 75%, more preferably by 10% to 50%. In some examples, the one ormore monomer and/or polymer controls the crystallinity of the polymericmaterial to between 1% and 55%, preferably between 1% and 35%. In someexamples, the one or more monomer and/or polymer does not change thecrystallinity of the polymeric material from being between 1% and 55%.The one or more monomer and/or polymer may not substantially change theTg of the polymeric material. Alternatively, the one or more monomerand/or polymer changes (increases or decreases) the Tg temperature ofthe polymeric material by 1° C. to 15° C., preferably 1° C. to 10° C.,more preferably by 1° C. to 5° C. In an example, the one or more monomerand/or polymer controls the Tg temperature of the polymeric material tobetween 20° C. and 55° C., preferably to between 35° C. and 50° C., morepreferably to between 37° C. and 50° C., most preferably between 37° C.and 45° C.

In some examples, the tubular body, degradable stent or stent maycomprise at least one non-degradable polymer where the polymer may bemodified to have the desired crystallinity, Tg, recoil, strength,shortening, expansion characteristics, crimping characteristics,molecular weight, and/or other characteristics. Non-degradable polymersinclude for example, a silicone-urethane copolymer, a polyurethane,poly(ethylene), phenoxy, ethylene vinyl acetate, chondroitinsulfatepoly(vinylidene fluoride), poly(vinylidene fluoride-co-hexafluoropropene), poly(tetrafluoroethylene), expanded poly(tetrafluoroethylene),poly(sulfone), polymethylmethacrylate, poly(n-butyl methacrylate),poly(N-vinyl pyrrolidone), copolymers of vinyl monomers and olefins suchas poly(ethylene-co-vinyl alcohol) (EVAL), copolymers ofacrylonitrile-styrene, ABS resins, and copolymers of ethylene-vinylacetate, poly(amides) such as Nylon 66 and poly(caprolactam), alkydresins, poly(oxymethylenes), poly(imides), poly(ester amides), epoxyresins, polyurethanes, rayon, and rayon-triacetate.

In some examples, the tubular body, biodegradable stent or stent maycomprise at least one degradable or non-degradable biological moleculewhere the material may be modified to have the desired recoil, strength,shortening, expansion characteristics, crimping characteristics,molecular weight, and/or other characteristics. Biological materialsinclude, for example, albumin, fibrin, fibrinogen, starch, poly(aminoacids), peptides, proteins, gelatin, elastin, chondroitin sulfate,dermatan sulfate (a copolymer of D-glucuronic acid or L-iduronic acidand N-acetyl-D-galactosamine), collagen, hyaluronic acid,glycosaminoglycans, polysaccharides, chitin, chitosan, cellulose,cellulose acetate, cellulose butyrate, cellulose acetate butyrate,cellophane, cellulose nitrate, cellulose propionate, cellulose ethers,and carboxymethylcellulose; and any derivatives, analogs, homologues,congeners, salts, copolymers and combinations thereof.

In some examples, the tubular body, biodegradable stent or stent maycomprise at least one degradable metal where the degradable metal has adesired recoil, strength, shortening, expansion characteristics,crimping characteristics, molecular weight, and/or othercharacteristics. Degradable materials for the metal stent include can bea suitable metal such as magnesium, zinc, iron, and alloys orcombinations thereof. The metal can be modified to exhibit differenthardnesses, and thus varying stiffnesses, by well-known annealing andmanufacturing processes. The tubular body may also comprise combinationsof biodegradable polymeric materials and degradable metals.

The degradable stent prosthesis may comprise a metal or metal alloy,optionally formed from a tubular body, wherein the metal or metal alloycomprises zinc, magnesium, and/or iron, or alloys, wherein the stent istreated to modify at least some abluminal surface regions making themconcave substantially across the width of said abluminal surfaceregions, and/or modifying at least some of side surface regions makingthem substantially convex across the thickness of said side surfaceregions.

The above surface region modification may be performed withoutsubstantially changing weight or mass of the prosthesis compared to theweight or mass of the prosthesis before treatment, or without losingmore than 15% in weight or mass after treatment, or withoutsubstantially losing more than 25% in weight or mass after treatment.

In some examples, the surface modification treatments is formed on astent substantially free from pits, holes or grooves. In some examples,the structural elements prior to treatment and following treatment aresubstantially free from pits, holes or grooves. In some examples, asubstantially rectangular cross section or a substantially square crosssection of the structural elements prior to treatment becomes anon-rectangular cross section or non-square cross section aftertreatment. In some examples, a substantially square or substantiallyrectangular cross section of the structural elements prior to treatmentbecomes a dogbone, dumbbell, barbell, elliptical, oval or racetrackshaped cross section after treatment. The surface treatment to modifythe shapes of the structural elements smoothes the surface regionsand/or removes roughness, burrs, sharp edges or corners that would catchon the catheter or vessel wall upon delivery or deployment. Followingthis treatment, the stent prosthesis is substantially smooth and freefrom roughness, burrs, sharp edges or corners that would catch, pierceor injure the vessel wall upon delivery or deployment.

Degradable metal and metal alloys can be treated using the methodsdescribed in this application. In addition, treatments using acid suchas nitric acid, hydrochloric acid, phosphoric acid and/or sulfuric acidcan be used to modify the abluminal surface regions to concave, and sidesurface regions to convex.

1. Structure Shaping by Solvent Treatment

The stent structures may be shaped by exposure to at least one solvent.The exposure to the solvent can be accomplished in a variety of wayssuch as by dipping, spraying, exposure to solvent vapor or other solventapplication processes.

a. Structure Shaping by Solvent Dipping

The stent supported lightly on a mandrel is dipped into a first solventfor about 1 second to one minute, 1 second to 30 seconds, or 2 secondsto 10 seconds and is quickly removed. The stent can be rinsed in asecond solvent to remove materials that are adhering to the stent. Thesolvent, solvent concentration, and time of exposure may be selectedbased on its ability to move the stent material at the side surfaceregions of the stent to the luminal and abluminal surface regions andchange the shapes of these surface regions without substantiallydissolving the stent, that is without the polymeric material dissolving(or otherwise dispersing) in the solvent and without forming a solutionof polymeric material in the treatment solvent. Also the solvents,concentrations and/or combinations of solvents and time of exposure maybe selected based on the particular polymeric materials utilized toachieve the desired shaping of the stent structural elements. At least aportion of the surface regions on the side, abluminal and luminalsurface regions of the struts and other structures can be shaped byinserting a loose mandrel such as a Teflon rod or tube inside the stentto support the stent during the selected treatment process. Preferably,the outer diameter of the loose mandrel is 0.001″ to 0.100″ smaller,more preferably 0.005″ to 0.015″ smaller than the inner diameter of thestent for a 2.5 to 4.0 mm stent.

At least some parts of the stent structure width may change by up to25%, preferably change by up to 15%, more preferably change by up to10%. In some examples, at least some parts of the stent structurethickness change by up to 25%, preferably change by up to 15%, morepreferably change by up to 10% as a result of the treatment.

The stent cross section may be reduced in width and increased inthickness due to the transfer, flow, or movement of stent polymericmaterial during the solvent shaping process. In some examples, theprocesses of shaping the surface regions of the stent can increase themaximum thickness of the stent by at least at least 2%, at least 5%,10%, at least 20%, or at least 30%, when taken in cross section. In someexamples, the change in thickness after treatment is 2 to 35micrometers, preferably 2-20 micrometer, and most preferably 4-10micrometers. The maximum width of the struts and other structures canremain the same while the thickness changes as described above or candecrease by at least 2%, at least 5%, at least 10%, at least 20%, or atleast 30%, when taken in cross section. The treatment may cause the flowof polymeric material from one side surface region to an immediatelyadjacent surface region, which may be on the same strut, crown or link.

In some examples, a change in width after treatment is 2 to 35micrometers, preferably 2-20 micrometer, and most preferably 4-10micrometers. In some examples, the treatment causes an initial diameterof the formed prosthesis to decrease to a smaller diameter, or apatterned diameter of the stent prosthesis to decrease to a smallerdiameter. For example, the inner diameter of the prosthesis aftertreatment can be reduced by an amount of 0.05 to 3 mm, preferably 0.1 to2 mm, most preferably 0.1 to 1 mm.

In some examples, the treatment does not substantially change anglesbetween the struts or structural elements. In other examples, the anglesbetween the struts or structural elements change by becoming smaller inan amount ranging from 1 to 75 degrees, preferably 2 and 50 degrees,most preferably 2 and 10 degrees. In other examples, the angles betweenthe struts or structural elements change by becoming larger in an amountranging from 1 to 75 degrees, preferably 2 and 50 degrees, mostpreferably 2 and 25 degrees.

In some examples, the treatment causes a change in length of the strutsor structural elements which ranges between 0.1 and 5 mm, preferably 1to 2 mm. In other examples, the treatment causes a shrinkage in lengthof the struts or structural elements in the range of 1% to 20%,preferably 1% to 15%.

In some embodiments, the shaping process can also be due toredistribution of the stent material from some surface regions of thestent to other surface regions to create the shaped struts with convexside surface regions and concave abluminal surface regions. The solventis selected and applied for periods of time to soften the polymericmaterial without dissolving it so that it flows from one surface regionto another portion of the surface region or an adjacent surface region.

In some embodiments, the stent mass after shaping process and removal ofsubstantially all of the solvent is substantially unchanged from beforethe treatment process. In some embodiments, the stent mass after theshaping process is decreased by no more than 25%, preferable no morethan 10%, more preferably no more than 5%. In some embodiments, afterthe treatment process with solvent and removal of substantially all ofthe solvent, the weight of the stent is substantially the same. Inanother example, the amount of solvent remaining in the polymericmaterial after treatment with solvent and removal of solvent rangesbetween 100 parts per million and 10,000 parts per million (PPM),preferably ranging between 1000 parts per million and 5000 parts permillion. In some examples, the amount of solvent remaining in thepolymeric material after removal of solvent ranges between 10-1000micrograms, preferably ranges between 10 and 100 micrograms.

The first and second solvent can be a single solvent or a mixture ofdifferent solvents. Examples of the first solvent include methylenechloride (DCM), chloroform, tetrahydrofuran, dimethyl-sulfoxide (DMSO),acetone, toluene, xylene, DMF, or the like, or a combination thereof.The first solvent may be any solvent which can dissolve the stent ifexposed to this solvent for more than 1 minute at room temperature. Thesecond solvent can be any solvent or other fluid which does notmeasurably dissolve the stent if the stent is exposed to the secondsolvent for more than 1 minute at room temperature. In order to providethe shaping without dissolving the polymeric material or losing anysignificant amount of the polymeric material, the treatment times areabout 0.1 second to one minute, 1 second to 30 seconds, or 2 seconds to10 seconds followed by removal from the solvent.

In a preferred embodiment, the stent material is not dissolved (i.e. notpermanently removed from the stent prosthesis) wherein the polymericmaterial flows from one surface region on a stent structural element toan adjacent surface region on the same stent structural element, or onesurface region on a stent structural element to the same surface regionon the same stent structural element.

The first solvent can also be a combination of a solvent that is capableof dissolving the stent and a solvent that does not dissolve the stent.For example, the first solvent can include a solvent capable ofdissolving the stent after 1 minute or longer of exposure to the solventat room temperature and a solvent which does not dissolve the stentafter 1 minute of exposure at room temperature. One example of such afirst solvent combination is 4 parts DCM and 6 parts Ethanol. In someexamples, the first solvent includes from 0.1 to 10 parts of solventcapable of dissolving the stent (such as DCM) and 9.9 parts to 0.1 partsof solvent not capable of dissolving the stent (such as Ethanol). Thesecond solvent can be ethanol, methanol, isopropanol, water, aqueoussolution, or the like, or combinations therefore.

The stent shaping process may utilize a mixture of solvents to modifythe stent structure cross section due to the transfer of stent materialfrom its width to its thickness.

The stent shaping process may utilize at least one solvent to initiatethe modification of the stent structure cross section due to thetransfer of stent material from its width to the thickness and at leastanother solvent to terminate the process.

Instead of using a second solvent, the stent on a mandrel can be shakenor blown with gas to remove excess solvent and/or dried in vacuum, oven,and or pressurized CO₂. Instead of a second solvent, the stent can bequickly placed in an oven, vacuum oven, freeze dried or exposed toanother known process to remove the first solvent.

Not all of the first or second solvent needs to be removed after thedipping treatment is complete. Additional processes which can be used toremove solvent include heat treatment, exposure to carbon dioxide,freeze drying or vacuum. The stent can be transferred to a bigger,tighter mandrel to maintain the dimensions of the stent for additionaldrying such as drying at ambient temperature, elevated temperature, suchas below the glass transition temperature of the polymer in an oven,vacuum oven, freeze drying or the like, in a vacuum, or other means.

The stent can also be further treated by placing on a tight mandrel anddipping to further shape the abluminal and side surface regions as willbe described further below. Additional shaping of the side, abluminaland luminal surface regions of the crowns and axial struts can beachieved by repeating a dipping treatment more than once or by dippingfor longer periods of time. Agitating during the dipping treatment canincrease the rate of shaping. Spinning or rotating of the stent in thesolvent can help achieve a more consistent application of the solventalong the length of the stent and particularly in tight spaces of thestent. Spinning can also change the distribution of the material duringshaping, for example to provide a strut shape with a wider abluminalside due to forces on the outer material of the stent during spinning.The stent can be treated while oriented in the solvent horizontally,vertically, at an angle or in a combination of orientations to achieve adesired shaping.

The stent may be rotated around its own axis and/or revolved around in achamber with solvent to control the shaping of the stent structure crosssection.

As an alternative or additionally to spinning or rotating the stent, thesolvent media can flow relative to the stent, or a combination ofrotating the stent and causing solvent to flow can be used to achievethe desired effect. The stent and the solvent can both move relative toeach other. Examples of this would be a revolving stent on a rotatingmandrel in a solvent bath which is being stirred with a stir bar.

FIGS. 2A-2C illustrate cross sections of stent structural elements aftertreatment according to some examples. In these figures, the treatmentprovides a concave abluminal surface region across substantially thewidth of the abluminal surface region; it also provides convex sidesurface regions across the thickness of the side surface regions. Theseshapes allow the distribution of tensile and compressive stresses over agreater area as shown in FIG. 12. As shown in FIG. 12, the surfaceregion area over which the tensile and compressive stresses aredistributed during bending of the stent structural element is increaseddue to the convex side surface regions and this leads to increasedradial strength of the stent. In some examples, a stent with modifiedcross section has increased radial strength by at least 5%, at least 10%or at least 20% over stents without modified cross section. Thetreatments described herein can increase the radial strength of thestent by at least 5%, at least 10% or at least 20%.

The first and second solvents and the processes for dipping and removingsolvent can vary depending on the desired stent cross sectional shape.

One advantage of the abluminal shaping is the increased drug delivery tothe walls of the lumen which can be achieved with a concave abluminalsurface region. The abluminal concave surface region can help directdrug delivery to the lumen wall. The edges of the concave abluminalsurface regions such as those shown in FIGS. 2A-2C can have a ledge orlip which further helps to direct drug delivery to the lumen wall. Thisfocuses drug delivery using concave abluminal surface regions.

b. Luminal and Side Shaping by Solvent Dipping

Shaping of or enhancing the luminal shape and/or shaping the sidesurface regions of the stent struts, crowns and other structures withoutabluminal shaping can be achieved by placing a tube such as Teflon tubeover the stent (or otherwise masking the surface areas not to betreated). The outer tube should be tight fitting so that no significantamount of fluid can pass between the outer surface regions of the stentand the inner surface region of the tube. Optionally, a looser mandrelsuch as a Teflon rod or tube can be inserted inside the stent as asupport for handling purposes. Preferably, the outer diameter of thislooser inner mandrel is 0.001″ to 0.100″ smaller, more preferably 0.005″to 0.015″ smaller than the inner diameter of the stent. The stentsheathed with the outer tube and supported lightly on the inner mandrelis then dipped into a first solvent for about 1 sec and quickly removedand preferably rinsed in a second solvent to remove materials that areadhering to the stent according to any of the methods and with any ofthe solvents described above with respect to the previous processes.

Shaped luminal surface regions and shaped side surface regions canprovide an improved surface region for contact with a delivery system,such as a balloon catheter. The convex side surface regions providegreater contact than square or rectangular flat surface regions betweenballoon material of the delivery system and the stent. FIG. 13illustrates a balloon with a pair of stent structural elements 110having modified luminal surface regions and convex sides and a pair ofstent structural elements 112 having flat surface regions. In theprocess of crimping the stent onto the balloon a portion or flap ofballoon material extends between the stent structural elements. As canbe seen in FIG. 13, there is increased surface region area of contactbetween the modified stent structural elements 110 with convex sides andthe balloon flap than with the flat surface regions of the stentstructural elements 112. This provides improved stent retention on aballoon catheter in a crimped configuration by using a shapingprocessing step.

Additionally, the concave luminal surface regions of the stentstructures can also improve stent retention on a balloon or otherdelivery system by providing a form of suction or vacuum surface regionwhich adhere the modified stent better to the balloon.

c. Solvent Vapor Shaping

The stent can be exposed to vapors of a solvent for an amount of timesufficient to provide a desired shaping of the stent structures. In thesolvent vapor shaping method, the stent is placed adjacent to a bath ofliquid solvent in a solvent chamber. The solvent is selected to be asolvent which can dissolve the stent at least in part if the stent isplaced in the solvent for one minute. However, in this method, it is thevapors from the solvent which come in contact with the crowns, axialstruts and other portions of the stent and redistribute the material ofthe stent to provide convex side surface regions, concave luminal and/orabluminal surface regions. The solvent or the entire vapor chamber canbe heated to accelerate vaporization of the liquid solvent in the liquidbath. Alternatively, the solvent vapor can be provided into the chamberin a gaseous form alone or with other gases. The time of exposure of thestent to solvent vapor can be greater than 10 mins, greater than 30mins, greater than 1 hour, greater than 24 hours, or greater than 48hours.

In some examples, the stent may be rotated around its own axis andrevolved around in a chamber with solvent vapor to control the shapingof the stent structure cross section.

After the solvent vapor shaping process is complete, excess solvent canbe removed by a second solvent, heating, drying or any of the methodsdiscussed herein. In some examples, the solvent chamber can bepressurized to increase the amount of solvent vapor in contact with thestent.

The exposure of only a portion of the stent to the solvent vapor, suchas by inserting a tight tube inside the stent or inserting the stentinside a tight tube (or any other suitable form of masking) canpreferentially shape the surface regions on the luminal or abluminalsides of the stent. Other masking methods can also be used.

The solvents employed in the solvent vapor smoothing process can includeany of the solvents described above. Particularly useful solvents arethose that can be provided in a gaseous form at a temperature of lessthan the Tg of the stent material.

d. Solvent Spraying

The stent can be exposed to solvent by spraying with the solvent toshape the surface regions of the stent structural elements andredistribute the stent material. Spraying of solvent can be performedwith any spray apparatuses, such as those that are known for applicationof drug/polymer coatings to stents. The sprayed solvent may be any ofthe solvents described herein which are capable of dissolving a portionof the stent structure.

Solvent spraying from an exterior of the stent can result inpreferential shaping with the abluminal surface regions experiencinggreater concave shaping than the luminal surface regions. In someexamples, abluminal surface regions have a concave radius of curvaturegreater than luminal surface regions. Solvent spraying can also be froman interior of the stent by passing a spray nozzle into the interior ofthe stent and moving it along the length of the stent interior. Maskingof portions of the stent may also be used to get preferential shaping ofsome surface regions over other surface regions.

In some examples, a flow rate of solvent sprayed onto the stent ishigher than typically use for coating a stent. Flow rates of at least 20ul/min (microliter/minute), at least 30 ul/min, or preferably at least75 ul/min, or more preferably at least 100 ul/min can be used.

A loose mandrel can be placed inside the stent during spraying tomaintain the shape of the stent as the solvent is sprayed onto thesurface regions.

The stent can be rotated and/or moved longitudinally during spraying. Insome examples, the stent is rotated and moved in a crisscross fashionduring spraying to achieve uniformity of shaping and to prevent largeamounts of material from being dissolved or redistributed too quickly.Air can be blown at the stent to remove any excess solvent during and/orafter spraying of the solvent. Removal of excess solvent can beperformed by any of the processes described herein.

e. Other Solvent Application

In addition to application of solvent by dipping, spraying, orapplication of solvent vapor, solvent can be applied to a stent toprovide shaped stent in other manners including ink jet printing,painting, gel application or the like.

Some of the solvent application methods described herein can applysolvent only to portions of the stent while leaving other portions ofthe stent untreated such as preferentially shaping and/or smoothing onlythe luminal or only the abluminal surface regions. In some examples, thetreatment is applied only to the crowns to further enhance the convexside surface regions of the crowns as these are the areas most likely toaffect tracking of the stent through the vasculature. The treatment canalso be used to preferentially treat different longitudinal sections ofthe stent to achieve a stent with differing performance along itslength. In some examples, the ends of the stent are treated to achieve astent with greater radial strength at the stent ends.

Treatment including heating and/or solvent treatment to provide thedesired shaped stent abluminal, luminal and side surface regions may beperformed before or during patterning of a stent, such as during lasercutting, or after patterning of the stent. One or more treatments oradditional treatments may be performed sequentially, or combined withother treatment processes, such as a heating and solvent treatmentprocess combined, to enhance or control the treatment process.Treatments include heating such as heating in an oven, heating byapplication of a hot gas stream, freeze drying, cooling byrefrigeration, fast cooling with liquid nitrogen, vacuum processing ordrying by application of an inert gas may be used before, during, orafter shaping treatment process. These treatment or additionaltreatments may be used to shape the material, remove solvents, soften orharden the polymeric material for treatment, and/or stabilize thetreated stent.

2. Media Blasting

Shaping of the stent surface regions can also be performed by materialremoval or material compacting from the stent by various media blastingtechniques. Material removal from or compacting of the stent crowns oraxial struts of a stent to create convex side surface regions, andconcave abluminal surface regions can be achieved using equipment suchas a sandblaster, media blasting machine, or similar equipment whichpropels particles at the stent. The blasting treatment propels small,abrasive particles toward the stent in a particular pattern whichmatches the regions of the stent to be shaped.

Examples of particles which can be used include evaporable particles,such as dry ice, salt, sugar, sodium bicarbonate, combination thereof,or the like which will either vaporize or can dissolve in water. The useof dry ice or another evaporable particle as the media particles whichwill turn gaseous at ambient temperature eliminates the need for removalof the blasting particles after the surface region shaping process. Insome examples, the evaporation of the evaporable particles may beassisted by application of heat, vacuum, or the like. The use of dry iceas the media particles can eliminate the need for removal after theshaping process because the dry ice will turn gaseous at ambienttemperature.

Other blasting media can include polymeric particles such aspolyethylene, polypropylene, polyethylene glycol, polyvinyl alcohol,polyvinylacetate, polyvinyl chloride, cellulose, copolymers of these,combination thereof, or the like which will dissolve in a solvent thatdoes not immediately dissolve the stent such as ethanol, methanol,propanol, THF, acetone, or the like. Exposure to solvent after blastingwith polymeric particles can remove particles that become at leastpartially embedded on the surface region of the stent. The mediaparticles preferably can dissolve in a solvent in a period of less than1 minute and the solvent is selected such that the stent does notdissolve in the solvent when the stent is exposed to solvent for 1minute or longer.

A size of the blasting particles using screened mesh sizing can rangefrom 60 to 600 mesh, from 100 to 550 mesh, or preferably from 150 to 500mesh. The mesh sizes referenced herein are from standard mesh sizes,such as US Sieve Series and Tyler Mesh Size, used to classify particlesize.

The size of the blasting particles impacting the surface region of thestent range from 250 micrometers to 10 micrometers, preferably from 100micrometers to 20 micrometers, more preferably from 50 micrometers to 25micrometers.

In some examples, instead of focusing the blasting particles on the edgeduring sandblasting, a mask can cover the majority of the stent surfaceregion but exposes only a portion of the edges of the crowns or axialstrut. The mask can be applied by ink jet printing technologies. Thecovered stent is then sandblasted to remove only material on the edge.Preferably sandblasting is done at an angle. The mask can then beremoved by any known means, such as by application of a solvent whichdissolves the mask without dissolving the stent. After removal of themask the resulting convex side surface regions and concave luminal andabluminal surface regions are exposed.

The media blasting may compact the material to provide the desiredshapes without removing a substantial amount of the polymeric materialfrom which the stent is formed.

3. Abrasive Tumbling

The stent surface regions can be shaped by abrasive tumbling methods.The stent can be placed in a tumbler, shaker, or vibrator with a lappingmedia, a sandblasting media, abrasives, abrasive grit, liquidlubricants, dry ice, others, or combination thereof, to form concaveabluminal surface region having radii of curvatures of about 0.030 toabout 0.200 mm, about 0.040 to about 0.150 mm, or about 0.040 to about0.100 mm. Examples of abrasive media include aluminum oxide, jeweler'srouge, optician's rouge, emery, silicon carbide, diamond, glass, metal,oxides, ceramics, or the like. In the abrasive tumbling methods, one ormore stents are placed inside a barrel or tumbler which is placed onslowly rotating rails which rotates, shakes, or vibrates the barrel. Thestents within the barrel slide past each other, with the lapping media,sandblasting media, abrasives, abrasive grit, liquid lubricants, others,or combination thereof, between them. The amount and speed of theshaping depends on the coarseness of the abrasive, and the duration ofthe tumble, shaking, or vibrating.

The stents can be cooled to make the material more brittle. The stentcan be cooled to a temperature below 10 degrees Celsius, preferablybelow 0 degrees Celsius, more preferably below −50 degrees Celsius usingdry ice or liquid nitrogen before and/or during tumbling.

The stents can be heated to make the material softer. The stent can beheated to a temperature above Tg before and/or during tumbling.

In some examples, a mask can be applied by ink jet printing technologiesor another known process to allow selective abrasive shaping of thestent surface regions. The masked stent is then tumbled to remove onlymaterial on the selected portions. The mask can then be removed by anyknown means, such as by application of a solvent which dissolves themask without dissolving the stent. After removal of the mask theresulting convex side surface regions and concave luminal and abluminalsurface regions are exposed. As in the other shaping processed describedherein, selective portions of the stent can be shaped without shapingother portions of the stent by use of mandrels, sleeves and/or masking.

4. Mechanical Shaping, Molding, Stamping and Ink Jet Printing

The surface regions of crowns, axial struts, or other stent structuresof a stent can be shaped or chamfered by certain mechanical tools toform shaped surface regions. The surface regions can be shaped orchamfered with a miniature tool having a sharp edge or deburring brushand small enough to fit between crowns and axial struts and scraping thetool across the surface regions. These tools can be moved roboticallyand controlled by a camera and an image processing system.

In some examples, the tool can be a rotating miniature sanding toolwhich by spinning against the surface regions or edges of the crowns oraxial struts creates convex side surface regions, concave luminalsurface regions and/or concave abluminal surface regions.

In order to increase the hardness of polymer stents or other stents ofsoft materials for mechanical shaping according to any of the describedprocesses, the stent can be held at a temperature below 10 degreesCelsius, preferably below 0 degrees Celsius, more preferably below −50degrees Celsius using any suitable cooling method such as dry ice orliquid nitrogen.

The abluminal surface regions of the crowns of a stent can be shaped orchamfered by inserting a curved or flexible mandrel inside the stent.The stent in the curved position on the mandrel is then dragged over anabrasive material such as sandpaper wrapped around a cylinder, roundfile, deburring brush, sanding stone, or the like. As the stent in acurved position is abraded against the surface region of the abrasivemeans, the leading edge of the crowns will be chamfered, beveled ordeburred.

An inside surface region of the stent can be processed to shape theluminal surface regions of the crowns, struts and other stent structuresby inserting a flexible abrasive means through the interior of thestent.

Ink jet printing technologies can also be used to build up some portionsof the stent or the stent to achieve concave luminal and abluminalsurface regions and convex side surface regions of the stent structures.As an example, a dispenser nozzle (or ink jet print head or cartridge orreservoir therefor) may be filled with a polymeric material solution oran extrusion nozzle loaded with a solid rod of the polymeric material.The nozzle may then be positioned close to the surface region of anobject such as a mandrel (optionally substantially round mandrel,preferably a 3-D patterned mandrel of the stent pattern desired)providing a former which together with control of the dispenser nozzleenables material to be deposited onto the mandrel to form a stentembodying the invention. For example, the mandrel may have approximatelythe deployed or optionally larger than the intended deployed diameter ofthe stent (labeled or nominal) or optionally 1.1-1.5 times larger thanintended deployed diameter of the stent, and optionally the mandrel mayhave the inner (luminal) surface region shape of the stent and thedispenser nozzle may be controlled to dispense or extrude the polymer asthe mandrel is rotated. In addition, the nozzle or the mandrel can bemoved radially and or axially by a 3-axis motion controller. The polymermay be dispensed or extruded from the nozzle in a preprogrammed stentpattern and the dispensing of the polymer be controlled to vary theshape of surface regions to provide straight, concave and/or convexshaped surface regions as describes throughout this application. Forexample, one or more layers or traces of polymeric material can be laiddown on top of each other to achieve a certain structural elementsthickness. Also, the width of the layer or trace may be adjusted, tomake it narrower. The nozzle may then dispenses or extrudes thepolymeric material along one side of the initial trace and then repeatfor the other side to achieve an abluminal concave surface region andthe sides of the struts forming a convex surface region. The stent maybe either left to dry, vacuumed, heat set, left to cool, or the like, ora combination thereof. Afterwards, the stent may be removed from themandrel by swelling the stent with solvent such as ethanol, acetone,tetrahydrofuran, methylene chloride, or the like, or a combinationthereof. After removal, the stent can be left to dry, vacuumed, heatset, left to cool, or the like, or a combination thereof. The stent mayor may not be coated with a polymer-drug matrix, crimped on a deliveryballoon catheter, packaged, and sterilized.

It should be appreciated that the stent structural elements or the stentitself may be manufactured so that the required surface regions have therequired shape. As an example, the stent structural elements or thestent itself may be manufactured by way of ‘3D printing’ whereby athree-dimensional model of the stent structural elements or the stentitself is supplied, in machine readable form, to a ‘3D printer’ adaptedto manufacture the stent structural elements or the stent itself. Thismay be by additive means such as extrusion, deposition, Electron BeamFreeform Fabrication (EBF), granular materials binding, lamination,photopolymerization, or stereolithography or a combination thereof or bya removal process such as ablation or cutting. The machine readablemodel may comprise a spatial map of the object to be printed, typicallyin the form of a Cartesian coordinate system defining the object'ssurface regions. This spatial map may comprise a computer file which maybe provided in any one of a number of file conventions. One example of afile convention is a STL (STereoLithography) file which may be in theform of ASCII (American Standard Code for Information Interchange) orbinary and specifies areas by way of triangulated surface regions withdefined normals and vertices. Another file format is AMF (AdditiveManufacturing File) which provides the facility to specify the materialand texture of each surface region as well as allowing for curvedtriangulated surface regions. The mapping of the stent structuralelements or the stent itself may then be converted into instructions tobe executed by 3D printer according to the printing method being used.This may comprise splitting the model into slices (for example, eachslice corresponding to an x-y plane, with successive layers building thez dimension) and encoding each slice into a series of instructions. Theinstructions sent to the 3D printer may comprise Numerical Control (NC)or Computer NC (CNC) instructions, preferably in the form of G-code(also called RS-274), which comprises a series of instructions regardinghow the 3D printer should act. The instructions vary depending on thetype of 3D printer being used, but in the example of a moving printheadthe instructions include: how the printhead should move, when/where todeposit material, the type of material to be deposited, and the flowrate of the deposited material.

The stent structural elements or the stent itself as described hereinmay be embodied in one such machine readable model, for example amachine readable map or instructions, for example to enable a physicalrepresentation of said stent structural elements or the stent itself tobe produced by 3D printing. This may be in the form of a software codemapping of the strut and/or crown and/or instructions to be supplied toa 3D printer (for example numerical code).

Molding, over molding or compression of a preformed part in a shapedmold can also be used to form the stent with the shaped concave luminaland abluminal surface regions and convex side surface regions of thestent structures or to treat a stent to form the concave luminal andabluminal surface regions and convex side surface regions.

Stamping of a preformed tubular stent can also be used to treat thestent to form the desired shape such as shaped concave luminal andabluminal surface regions and convex side surface regions.

5. Laser Shaping

A laser can be used to shape the stent structures. With a laser havingthe ability to ablate with low energy and layer by layer, such as afemtosecond laser, a laser cutting program can be set to ablate adesired shape of the stent surface regions. In some examples, the lasercan be used to create concave luminal and abluminal surface regions andconvex side surface regions of the stent structures. A series of laserformed steps can create the convex side surface regions of the struts.In a similar manner, the laser can be used to create the concave luminalor flat or concave abluminal surface regions by a series of small stepsalong the surface region. The steps can be smoothed out with solvent,sandblasting, tumbling, or the like.

In some examples, a series of overlapping cuts, with each cut narrowerthan 35 micrometers, narrower than 30 micrometers, or narrower than 25micrometers can be made from the abluminal surface region to the sidesurface region of the stent structure to achieve the convex side surfaceregion on the crown, axial strut or other stent structure.

In some examples, the stent can be cut during the laser cutting processwith off-axis control such that the axis of the laser beam and the axisof the assist gas supply nozzle on the laser such as a femtosecond laseris eccentrically oriented. This allows the laser to cut material at anangle rather than straight cut, resulting in a curved surface region.This process can be used to form the curved surface regions describedherein.

The convex side surface regions of the stent can also be formed usingeither trepanning or helical drilling. Trepanning is a combined cuttingand drilling process, typically performed using a pulsed laser. Intrepanning, a through hole is first pierced by percussion drilling andthen in a second step the through hole is widened to its final diameterin a circular cutting motion by the laser. In a similar manner, thelaser beam can cut the material at an angle to form the curved surfaceregions. After a first cut at an angle to form the rounded top portionof the strut side surface regions, the laser can cut the rest of thestent pattern with a straight cut. This results in a partially convexside surface region. It is also possible to make the last part of thelaser at an angle so that side surface region is fully convex. Inhelical drilling, a rotational movement of the laser beam is used tocreate a positive or negative taper at the stent surface regions.

In some examples, where the stent is patterned from a tube by lasercutting and the stent is treated to form a dogbone, barbell, bulbous,elliptical, racetrack or other shape described herein by laser, theprocesses of patterning and shaping can be performed together.

6. Heat Shaping

As an example, the surface regions of stent can be melted by thermalenergy and the material can be redistributed to achieve the desiredshaping of the surface regions. In the thermal method heat may beapplied in an oven, for a duration and at a temperature to provideconvex side surface regions and/or concave luminal and abluminal surfaceregions. The heating temperature can be controlled to reach the meltingtemperature of the polymer at the surface regions to be shaped withoutreaching the melting temperature in the remainder of the stent material.

The temperature for heating a biodegradable polymer material, forexample a polylactide polymer or copolymer, for heat shaping can bebetween 50° C. and 180° C., preferably between 75° C. and 150° C. Insome examples, the heating temperature can be above Tg, preferably 30°C. to 100° C. above Tg. In some examples, the heating can be for 1minute to 5 hours, preferably 5 minutes to 4 hours. The temperature andtime of treatment may be adjusted and varied to accomplish the desiredtreatment and changes to the shape of the structural elements.

It should be appreciated that the required shape may be formed by addingmaterial to the surface region of the original stent structural element,removing from the surface region of the original stent structuralelement and/or moving material on the surface region of the originalstent structural element.

The amount of material added, moved and/or removed will be determinedbased on the original shape of the surface region of the stentstructural element and the required shape of the surface region of thestent structural element. Material may be removed from the outer edge,added to the central portion, moved from the outer edge to the centralportion, and/or moved from the outer edge to an adjacent side of thestent structural element to form a convex surface region. Material maybe removed from the central portion, added to the outer edge, moved fromthe central portion to the outer edge, and/or moved from an adjacentside to the outer edge of the stent structural element to form a concavesurface region.

It should be appreciated that various techniques may be used to removematerial from the structural elements so that the required surfaceregions have a concave and/or a convex shape. For example, material canbe removed from the surface region of a strut using techniques such asnegative ‘3D printing’, nanofabrication, microfabrication,photolithography, lithography, and etching.

The stent structural element may also be manufactured to the requiredshape. For example, the stent structural element may be extruded suchthat the profile of the stent structural element has the required shape.In some examples the stent prosthesis may be manufactured with stentstructural elements of the required shape using a molding process.

The convex side surface regions can also improve flexibility of thestent or stent. The stent with curved axial struts can bend in amultitude of directions compared to axial struts with flat surfaceregions. For example, a stent with rectangular axial struts or linkswill bend primarily in two preferred directions because of the flatsurface regions of the axial struts. The struts cannot bend in thedirection of the edge. However, modified strut cross sections withconvex sides provide more freedom to bend in multiple directions andthus provide a more flexible and deliverable stent or stent.

When the struts, crowns and/or other stent structures are coated with adrug for delivery to a lumen, convex side surface regions can providefor a more uniform drug coating and thus can release drug from asubstantially more uniform surface region than a square or rectangularstrut. Concave luminal and abluminal surface regions also can provideimproved directionality of drug delivery to the lumen or vessel wall.

For a substantially amorphous polymer material which is less than 15%,preferably less than 10% crystalline, solvent shaping of the tubularbody does not significantly alter the crystalline orientation of thematerial since the substantially amorphous material is random incrystalline orientation.

Convex side surface regions can also improve crimping of the stent orstent because convex structure sides are more resistant to overlappingstruts when crimped from a larger as-cut diameter to a smaller crimpeddiameter due to the absence of flat surface regions which can catch onone another during crimping. FIG. 14 illustrates an end view of acrimped stent with rectangular cross section stent structural elements120. The rectangular stent structural elements 120 can overlap and twistdue to crimping. The stent structural elements 130 of FIG. 15 havingcurved side surface regions can reduce or eliminate the overlapping andtwisting which occurs with flat rectangular surface regions. FIG. 15shows a stent body in cross section with convex side surface regions ofthe stent structural elements. Twisting and rotating of stent structuralelements along their axis can happen during expansion as well as duringcrimping. The convex side surface regions and concave abluminal surfaceregions prevent or reduce rotating of stent structural elements duringcrimping and/or during expansion to less than 45 degrees, less than 35degrees or less than 25 degrees.

Struts or other stent structures having shaped surface regions asdescribed above can be considered to have oblong, oval, elliptical, nearelliptical, circular, near circular, or dogbone like cross sectionalshapes. Where the shaping treatment is performed before application ofthe drug in a preferred embodiment, the drug coating process achieves aproduct with shaped surface regions as the coating process maintainssubstantially the same shape. In some examples, in at least some of thetreated structural elements where the concave luminal and/or abluminalsurface regions join convex side surface regions there is a lip or aledge which extends along at least some of the structural elements. Thelip or ledge may exist at or near one or more of the junctures of theluminal and/or abluminal surface regions and the side surface regions.The lips and or ledges may be between the abluminal and side surfaceregions or between the luminal and side surface regions such that thelip protrudes outwardly. These lips may extend continuously along astrut and a connected crown of the expandable stent prosthesis in theform of a lip, edge or wave. The thickest part of the cross-section of astructural element may be at the lip. FIG. 24 shows the abluminal lipsextending along a strut and along a crown. FIG. 27 shows a lip near oradjacent to the juncture of the luminal and side surface regions.

In some examples, the stent prosthesis cross section has concave luminaland/or abluminal surface regions and convex side surface regions whichform a continuous curve across the side surface regions to provide acontinuous convex curve in the form of an arc which extends betweenabluminal and luminal lips. In some examples, at least some abluminalsurface regions and at least some luminal surface regions join said sidesurface regions at a lip and a thickness between an abluminal lip and aluminal lip forms a thickest part of the cross section of saidstructural elements, while a thickness at a core or substantially amidpoint between the abluminal lips forms a thinnest part of the crosssection of said structural elements.

In some embodiments, the biodegradable stent prosthesis comprises a bodyhaving a plurality of rings each ring comprises a plurality of strutsjoined by crowns, wherein each ring is connected to an adjacent ring byat least one link.

In some embodiments, the biodegradable stent prosthesis comprises a bodyhaving a plurality of struts joined by crowns.

In some embodiments, the biodegradable stent prosthesis comprises a bodyhaving a plurality of rings connected by at least one link, and aplurality struts joined by crowns.

In some examples, the biodegradable stent prosthesis comprises a bodyhaving abluminal surface regions, luminal surface regions, and two sidesurface regions of each structural component of the stent, along thelength of the stent.

In some embodiments, the biodegradable stent prosthesis comprises apolymeric material forming a tubular body, wherein said body comprises astent pattern having a plurality of struts, crowns and optionally links,each having four surface regions, such that a cross section of saidstruts is rectangular having a concave abluminal surface region and/orconvex side surface region, and a cross section of said crown issubstantially rectangular having convex side surface regions and/oroptionally a concave abluminal surface region. The cross-section issubstantially rectangular in the sense that the dimensions of width andthickness are different.

Although rectangular and square cross sections having four sides aredescribed other cross sections have more than four sides or fewer thanfour sides are also contemplated.

In some embodiments, the biodegradable stent prosthesis comprises apolymeric material forming a tubular body, wherein said body comprises astent pattern having a plurality of struts, crowns and optionally links,each having four surface regions, such that a cross section of saidstruts is substantially square having concave abluminal surface regions,and/or convex side surface regions, and a cross section of said crown issubstantially square having convex side surface regions, and/oroptionally concave abluminal surface region. The cross-section issubstantially square in the sense that the dimensions of width andthickness are substantially the same.

The biodegradable stent prosthesis may be expandable from a crimpedconfiguration to an expanded larger configuration to support a bodylumen or a blood vessel.

The biodegradable stent prosthesis may be expandable from a crimpedconfiguration to an expandable larger configuration at body temperature.

The biodegradable stent prosthesis may be expandable from a crimpedconfiguration to an expandable larger configuration and have sufficientstrength to support a body lumen or a blood vessel.

The biodegradable stent prosthesis may be circumferentially expandablefrom a crimped configuration to an expanded larger configuration.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable polymeric material.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable metal or metal alloy.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable polymeric material, and a biodegradable metal or metalalloy.

In some embodiments, the biodegradable prosthesis comprises a degradablepolymeric material, said polymeric material is formed as a tubular bodyusing extrusion, dipping, spraying, or printing.

In some embodiments, the biodegradable stent prosthesis comprises adegradable metal or metal alloy, said metal or metal alloy is formed asa tubular body.

In some embodiments, an expandable biodegradable prosthesis comprises anexpandable prosthesis body formed from a biodegradable polymericmaterial, the expandable prosthesis body having a plurality of stentstructural elements each having luminal and abluminal surface regions.The plurality of stent structural elements includes a plurality ofcircumferentially expandable serpentine rings, each serpentine ringincluding axial struts joined by crowns. At least some of the abluminalsurface regions are concave across substantially the width of the stentstructural elements. The prosthesis is expandable from a crimpedconfiguration to an expanded larger configuration to support a bodylumen.

In some embodiments, the biodegradable stent prosthesis comprises adegradable polymeric material formed as a tubular body, said stent ispatterned into a structure comprising a plurality of rings, wherein eachring comprises a plurality of struts and crowns, wherein adjacent ringsare connected by at least one link, wherein the stent struts haveabluminal and luminal surface regions, wherein at least some of thestruts abluminal surface regions are concave across substantially thewidth of said struts.

In some embodiments, the biodegradable stent prosthesis comprises adegradable polymeric material formed as a tubular body, said stent ispatterned into a structure comprising a plurality of rings, wherein eachring comprises a plurality of struts and crowns, wherein adjacent ringsare connected by at least one link, wherein the stent struts haveabluminal and luminal surface regions, wherein substantially all of thestruts abluminal surface regions are concave across substantially thewidth of said struts.

In some embodiments, the biodegradable stent prosthesis comprises adegradable polymeric material formed as a tubular body, said stent ispatterned into a structure comprising a plurality of rings, wherein eachring comprises a plurality of struts and crowns, wherein adjacent ringsare connected by at least one link, wherein the stent struts haveabluminal and luminal surface regions, and at least one side surfaceregion between the luminal and abluminal surface regions, wherein atleast some of the struts abluminal surface regions are concave acrosssubstantially the width of said struts, and wherein at least some of thestruts side surface regions are convex across substantially thethickness of said struts.

In some embodiments, the biodegradable stent prosthesis is patternedinto a structure comprising a plurality of serpentine rings, each ringcomprises struts joined by crowns, and wherein adjacent rings are joinedby at least one link, said rings have abluminal and luminal surfaceregions, and two side surface regions between the luminal and abluminalsurface regions; wherein at least some of the rings luminal surfaceregions are concave across substantially the width of said ring, andwherein at least some of the rings side surface regions are convexacross substantially the thickness of said ring.

In some embodiments, the stent structural elements comprise side surfaceregions extending between the luminal and abluminal surface regions,wherein at least some of the side surface regions are convex.

In some embodiments, the expandable prosthesis body is formed from atube and the formed prosthesis body has been treated to form the concaveabluminal surface regions.

In some embodiments, the expandable prosthesis body is formed from aflat sheet and the formed prosthesis body has been treated to form theconcave luminal and abluminal surface regions.

In some embodiments, the treatment does not substantially change theweight or mass of the prosthesis body.

In some embodiments, the stent prosthesis is treated to form concaveshapes across substantially the width of the stent abluminal surfaceregions, and convex shapes across substantially the thickness of thestent side surface regions, wherein the weight or mass of the stentprosthesis before treatment and after treatment is substantially thesame.

In some embodiments, the stent prosthesis is treated to form concaveshapes across substantially the width of the stent abluminal surfaceregions, and convex shapes across substantially the thickness of thestent side surface regions, wherein the weight or mass of the stentprosthesis before treatment and after treatment are within 15% of eachother.

In some embodiments, the stent prosthesis is formed comprising concaveshapes across substantially the width of the stent abluminal surfaceregions, and convex shapes across substantially the thickness of thestent side surface regions, and wherein the weight or mass of the stentprosthesis before treatment and after treatment is substantially thesame.

In some embodiments, a method of forming an expandable polymerprosthesis with modified surface regions includes the steps of forming atubular expandable prosthesis with a plurality of stent structuralelements each having a luminal surface region, an abluminal surfaceregion and two side surface regions extending between said luminal andabluminal surface regions by patterning the prosthesis from a polymertube; and exposing the expandable prosthesis to a treatment for apredetermined period of time to modify the surface regions, whereinresulting modified abluminal surface regions are concave.

In some embodiments of the method the modified side surface regions ofthe expandable prosthesis are convex.

In some embodiments of the method the treatment changes the shapes ofthe surface regions and does not substantially change the weight or massof the prosthesis.

In some embodiments, an expandable prosthesis includes an expandableprosthesis body formed from a plurality of stent structural elementsincluding struts, crowns and optionally links, each having luminal andabluminal surface regions and side surface regions extending between theluminal and abluminal surface regions, wherein at least some of theabluminal surface regions are concave and wherein at least some of theside surface regions are convex, wherein said prosthesis is expandablefrom a crimped configuration to an expanded larger configuration tosupport a body lumen.

In some embodiments, the endoprosthesis is patterned from a tube bylaser cutting and the laser cut treatment forms the concave abluminalsurface regions and convex side surface regions. In some embodiments,the treatment comprises shaping by application of a solvent by at leastone of dipping, spraying, or contact with a solvent vapor.

In some embodiments, the treatment includes shaping by tumbling,agitating, deburring, scraping, or sandblasting. In some examples, theprocessing includes shaping with a laser or heat. The processing can befollowed by forming a coating of at least one drug formed over theexpandable endoprosthesis body.

In some examples, the endoprosthesis comprises a plurality ofcircumferentially expandable serpentine rings, each serpentine ringcomprises axial struts joined by crowns, wherein one crown joins twoadjacent axial struts of a serpentine ring, and wherein the crowns actas hinges allowing the struts to spread as the ring expandscircumferentially, at least one link joining adjacent serpentine rings.

The stent endoprosthesis may be formed from a biodegradable polymericmaterial which has a molecular weight ranging from 100 KDa to 1000 KDa.In some embodiments, the biodegradable polymeric material has an elasticmodulus of at least 0.35 GPa, preferably between 0.35 GPa and 1.5 GPa.

The biodegradable polymeric material may comprise one or more ofpolymers and copolymers. The endoprosthesis may be capable of beingexpanded from a crimped diameter to a deployed diameter at bodytemperature without fracture of the endoprosthesis.

The endoprosthesis may comprise a biodegradable polymeric materialcomprising one or more of: Lactide, poly-DL-Lactide,polylactide-co-gycolide, polylactide-co-polycaprolactone, poly(L-lactide-co-trimethylene carbonate), polytrimethylene carbonate,polyhydroxybutyrate, polyhydroxyvalerate, poly orthoesters, polyanhydrides, polylactide, polyglycolides, polycaprolactone, tyrosinederived polycarbonates, polyiminocarbonates, and copolymers thereof.

In some embodiments, the polymeric material comprises one or morepolymers or co-polymers, or polymer blends.

The prosthesis body may be formed as a tube and patterned by lasercutting.

The endoprosthesis is preferably balloon expandable.

In some embodiments, the endoprosthesis is self-expandable.

In some embodiments, the stent prosthesis is self-expandable and balloonexpandable.

In some embodiments, a polymer endoprosthesis comprises a tubularexpandable endoprosthesis body comprising a polymeric material which hasbeen patterned from a tube to form the stent, said stent comprises aplurality of stent structural elements each stent structural elementhaving a luminal surface region, an abluminal surface region, and twoside surface regions extending between said luminal and abluminalsurface regions, wherein at least one of the abluminal surface regionsis concave, and wherein the two side surface regions are convex.

A drug coating comprising at least one drug may be coated on at least aportion of the expandable endoprosthesis body. The at least one drug maybe contained within a coating, preferably a polymeric coating, coveringat least a portion of the stent prosthesis.

In an embodiment, a method of forming a polymer endoprosthesisprosthesis with modified surface regions comprises the steps of forminga tubular expandable endoprosthesis with a plurality of stent structuralelements each having a luminal surface region, an abluminal surfaceregion and two side surface regions extending between said luminal andabluminal surface regions by cutting the endoprosthesis from a polymertube and exposing the tubular expandable endoprosthesis to a treatmentfor a predetermined period of time to modify the surface regions,wherein the resulting modified abluminal surface regions are concavewhile the modified two side surface regions are convex.

In some embodiments, at least some of the abluminal surface regions ofsome portions of the polymeric prosthesis are concave and at least someof the side surface regions are concave.

In some embodiments substantially all of the abluminal surface regionsof the prosthesis are concave and substantially all of the side surfaceregions of the prosthesis are convex.

The treatment may change the shapes of the surface regions and notsubstantially change the weight or mass of the endoprosthesis.

The treatment process may not significantly dissolve the polymericmaterial from which the endoprosthesis is formed.

The treatment process may not substantially dissolve the polymericmaterial from which the endoprosthesis is formed.

In some example methods, the treatment does not dissolve more than 10%,more than 15% or more than 20% of the polymeric material from which theendoprosthesis is formed.

In some example methods, the treatment does not substantially degradethe polymeric material from which the endoprosthesis is formed eithermechanically or chemically.

Preferably, the treatment shifts polymeric material from at least onesurface region to an adjacent surface region without a substantialchange in weight or mass before and after treatment.

Preferably, the treatment shifts polymeric material from at least onesurface region to an adjacent surface region modifying at least someabluminal surface regions into concave shape and at least some sidesurface regions into convex surface regions without a substantiallychange in the weight or mass before and after treatment.

The treatment may shift polymeric material from abluminal and/or luminalsurface regions of the stent prosthesis to the side surface regions ofthe stent prosthesis (or vice versa), preferably without substantiallyloss of material, more preferably without weight or mass change of morethan 5%, most preferably without substantial change in stent weight ormass.

The treatment may shift polymeric material from at least one sidesurface region to one of luminal or abluminal surface regions of thestent prosthesis, preferably without substantially loss of material,more preferably without loss of more than 5%, most preferably withoutsubstantial change in stent weight or mass.

In some embodiments, a method of forming a polymer endoprosthesisprosthesis with a controlled strut thickness includes the steps offorming a tubular expandable endoprosthesis with a plurality of strutsby cutting the endoprosthesis from a polymer tube having a firstthickness, said endoprosthesis comprising a polymeric material andexposing the tubular expandable endoprosthesis to a solvent for apredetermined period of time to redistribute said polymeric materialwithout substantially dissolving it to adjust a thickness of theplurality of struts to a second thickness, wherein the second thicknessis greater than the first thickness.

In some embodiments, a polymer endoprosthesis includes a tubularexpandable endoprosthesis body comprising a polymeric material which hasbeen cut from a tube to form an endoprosthesis with a plurality of stentstructural elements each having a luminal surface region, an abluminalsurface region, and two side surface regions extending between saidluminal and abluminal surface regions, wherein the two side surfaceregions are convex and have a radius of curvature of at least 0.020 mm.

In some embodiments, a polymer endoprosthesis comprises a tubularexpandable endoprosthesis body comprising a polymeric material which hasbeen cut from a tube to form an endoprosthesis with a plurality of stentstructural elements each having a luminal surface region, an abluminalsurface region, and two side surface regions extending between saidluminal and abluminal surface regions, wherein the abluminal surfaceregions of the stent structural elements are shaped to form concavesurface regions extending substantially from one side surface region toan opposite side surface region; a coating comprising at least one drugformed over the tubular expandable endoprosthesis body. Preferably, acoating comprising a drug is coated over said abluminal surface regionwithout substantially changing the concave shape.

In some embodiments, a method of forming a polymer endoprosthesisprosthesis with a modified shape includes the steps of forming a tubularexpandable endoprosthesis with a plurality of stent structural elementshaving luminal, abluminal and side surface regions extending betweensaid luminal and abluminal surface regions by cutting the endoprosthesisfrom a polymer tube having a first thickness and treating the tubularexpandable endoprosthesis to increase a thickness of the plurality ofstent structural elements between the luminal and abluminal surfaceregions while decreasing a width of the stent structural elementsbetween the side surface regions by redistributing the polymer.Preferably, the treating increases the thickness of a plurality of stentstructural elements but the width of the stent structural elementsremains unchanged. The width and thickness may be measured as themaximum dimensions for the width and thickness, taken at the widest orthickest spot on the strut. Although the maximum dimensions can be used,the minimum, median, average or mean dimensions, or whatever isappropriate in the circumstances can be used for dimensions. The changesor no changes can be detected regardless of the measurement protocolselected.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable polymeric material formed as a tubular body, wherein saidtubular body is composed of an abluminal surface region, a luminalsurface region, and two side surface regions, wherein the tubular bodyis patterned into a structure having an abluminal surface region, aluminal surface region, and side surface regions, and wherein the stentis treated after patterning to shift polymeric material from at leastone side surface region to said luminal and/or abluminal surfaceregions.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable polymeric material formed as a tubular body, wherein saidtubular body is composed of an abluminal surface region, a luminalsurface region, and at least two side surface regions, wherein thetubular body is patterned into a structure having an abluminal surfaceregion, a luminal surface region, and at least two side surface regions,and wherein the stent is treated after patterning to shift polymericmaterial from at least some luminal and/or abluminal surface regions toat least one adjacent side surface region, wherein the at least saidtreated abluminal surface regions become substantially concave, andwherein the at least adjacent side surface regions become substantiallyconvex.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable polymeric material formed as a tubular body, wherein saidtubular body is composed of an abluminal surface region, a luminalsurface region, and at least two side surface regions, wherein thetubular body is patterned into a structure having an abluminal surfaceregion, a luminal surface region, and at least two side surface regions,and wherein the stent is treated after patterning to shift polymericmaterial from at least some side surface regions to at least oneadjacent luminal and/or abluminal surface region (or vice versa shiftingmaterial from luminal and/or abluminal to side), wherein the at leastsome treated abluminal surface regions become substantially concave, andwherein the at least some adjacent side surface regions becomesubstantially convex, and wherein the weight or mass of the stentprosthesis before and after said treatment is substantially the same.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable polymeric material formed as a substantially flat body,wherein said body is composed of an abluminal surface region, a luminalsurface region, and at least two side surface regions, wherein the bodyis patterned into a structure having an abluminal surface region, aluminal surface region, and at least two side surface regions, andwherein the stent is treated after patterning to shift polymericmaterial from at least some side surface regions to at least on adjacentluminal and/or abluminal surface region, wherein the at least saidtreated luminal and/or abluminal surface regions become substantiallyconcave, and wherein the at least adjacent side surface regions becomesubstantially convex, and wherein the weight or mass of the stentprosthesis before and after said treatment is substantially the same.

The surface region roughness of treated luminal, abluminal, and adjacentsides may be substantially reduced after treatment. For example, thesurface region roughness of treated luminal, abluminal, and adjacentside surface regions, may be substantially reduced after processtreatment. In some examples, the root-mean-square roughness (Sq) rangesbetween 0.5 micrometers to 15 micrometers. In another example theroughness average (Sa) ranges from 0.5 micrometers to 10 micrometers asmeasured by optical profilometry or atomic force microscopy.

The treated surface regions may increase crystallinity at the surfaceregion of the stent prosthesis by at least 15%.

The treated surface region may have a crystallinity that issubstantially different from the core of the treated stent prosthesis byat least 15%, or by at least 20%, or by at least 25%, or by at least30%. The crystallinity of the treated surface region within 25% depthfrom the treated surface region may be substantially different from thecrystallinity of the said core of the treated stent prosthesis.

In some examples, the crystallinity of the polymeric material aftertreatment including treatment to shape the structural elements canincrease at least 10% or at least 20%, or between 5% and 50% orpreferably between 5% and 30%. In some examples the crystallinity of thepolymeric material after treatment to shape the structural elements issubstantially the same.

The treatment may increase cross linking at the surface region of thestent prosthesis. Increased cross linking results in a stent whichabsorbs less solvent when exposed to the solvent. The increase in crosslinking results in absorption of solvent reduction by at least 10%.

The treated stent prosthesis surface region may have an increasedhydrophobicity. This is very helpful when coating the stent prosthesiswith a coating or a drug comprising a solvent wherein the absorption ofsaid solvent is reduced by at least 10%. It can also be helpful to delaysubstantially complete hydration of the stent prosthesis by at least 1minute.

When fabricating a biodegradable stent prosthesis, it is desirable todesign the prosthesis such that the stent design comprising stentstructural elements, for example crowns or/and struts, having width tothickness dimensions that are approximately 1:1, or range fromapproximately 0.8:1 to approximately 1.1:1, such that upon expansion ofthe biodegradable stent prosthesis said stent structural elements alongthe length of the stent prosthesis are substantially free from rotatingaround their axis, or substantially free from rotating more than 45degrees around their axis. This allows the stent prosthesis to haveimproved strength such as sufficient strength to support a body lumen,improved uniformity of expansion, and/or be free from fracture uponexpanding the stent from a crimped configuration to an expanded largerconfiguration.

However, such desire is difficult to achieve when using biodegradablematerial since the biodegradable material are typically weaker materialand therefore in order to achieve smaller thickness, the width of suchstent prosthesis stent structural elements, for example struts, will belarger than thickness, typically width to thickness ratio are at least1.2:1, and that contributes to having stent structural elements alongthe length of the stent prosthesis prone to rotating or twisting uponexpanding the stent prosthesis from a crimped configuration to anexpanded larger configuration, resulting in lower strength, loweruniformity of expansion, or strut and/or crown fracture, upon expansionof the stent or after expansion. It is therefore desirable to be able todesign a biodegradable stent prosthesis that is smaller in thickness,having a width to thickness ratio of at least 1.2:1 wherein the stentstructural elements upon expansion or after expansion are substantiallyfree from said stent structural elements rotating, or substantially freefrom rotating more than 45 degrees around their axis, or substantiallyfree from rotating more than 25 degrees around their axis. Such desirefor performance is achieved when fabricating a stent comprising stentstructural elements that have at least some of the luminal and/orabluminal surface region concave, and optionally at least some of thesides extending between said luminal and abluminal surface regionsconvex, said degradable stent prosthesis stent structural elements uponexpansion from crimped configuration to an expanded configuration aresubstantially free from rotating more than 45 degrees around their axis.

In an embodiment, the biodegradable stent prosthesis comprises abiodegradable polymeric material formed as a tubular body usingextrusion, dipping, spraying or printing, wherein the stent prosthesisis patterned into a structure comprising stent structural elements, suchas struts, wherein said stent structural elements having widths that areat least 1.2 times said stent structural element thickness, wherein thepatterned structure comprises luminal, abluminal, and side surfaceregions, wherein at least some of said stent structural elements havingconcave abluminal surface regions along the width of said stentstructural elements, and optionally wherein at least some of said stentstructural elements have at least one convex side surface regionextending between said abluminal and luminal surface region, said stentprosthesis is expandable from a crimped configuration to an expandedlarger configuration wherein the said stent structural elements remainsubstantially free from rotating.

In some embodiments, an expandable prosthesis includes an expandableprosthesis body formed from a plurality of stent structural elementseach having luminal and abluminal surface regions and side surfaceregions extending between the luminal and abluminal surface regions,wherein at least some of the luminal and abluminal surface regions areconcave and wherein at least some of the side surface regions areconvex, wherein said prosthesis is expandable from a crimpedconfiguration to an expanded larger configuration to support a bodylumen.

The endoprosthesis may be cut from a tube by laser cutting and the lasercut prosthesis has been processed to form the concave luminal andabluminal surface regions and convex side surface regions. As anotherpossibility, the processing includes shaping by application of a solventby at least one of dipping, spraying, or contact with a solvent vapor.

The endoprosthesis stent structural elements can include a plurality ofcircumferentially expandable serpentine rings, each serpentine ringincluding struts joined by crowns, wherein one strut joins two adjacentcrowns of a serpentine ring, and wherein the crowns act as hingesallowing the struts to spread as the ring expands circumferentially,links joining some but not all crowns on adjacent serpentine rings. Thetreatment may modify the surface regions of all of the stent structuresof the endoprosthesis.

In some embodiments, a polymer endoprosthesis includes a tubularexpandable endoprosthesis body comprising a polymeric material which hasbeen cut from a tube to form an endoprosthesis with a plurality ofstruts each having a luminal surface region, an abluminal surfaceregion, and two side surface regions extending between said luminal andabluminal surface regions, wherein at least one of the luminal andabluminal surface regions is concave and the two side surface regionsare convex

In some embodiments, a method of forming a polymer endoprosthesis withmodified surface regions includes the steps of forming a tubularexpandable endoprosthesis with a plurality of struts each having aluminal surface region, an abluminal surface region and two side surfaceregions extending between said luminal and abluminal surface regions bycutting the endoprosthesis from a polymer tube and exposing the tubularexpandable endoprosthesis to a treatment for a predetermined period oftime to modify the surface regions, wherein the resulting modifiedluminal and abluminal surface regions are concave while the modified twoside surface regions are convex.

The Tg of the polymer comprised in the polymeric stent after the shapingprocess may be substantially unchanged from before the treatmentprocess.

The crystallinity of the polymer comprised in the polymeric stent afterthe shaping process may be substantially unchanged from before thetreatment process.

The molecular weight of the polymer comprised in the polymeric stentafter the shaping process may be substantially unchanged from before thetreatment process.

The molecular number of the polymer comprised in the polymeric stentafter the shaping process may be substantially unchanged from before thetreatment process.

In the polydispersity index of the polymer comprised in the polymericstent after the shaping process may be substantially unchanged frombefore the treatment process.

In some embodiments, a method of forming a polymer stent prosthesis witha controlled strut thickness includes the steps of forming a tubularexpandable prosthesis with a plurality of struts by cutting theprosthesis from a polymer tube having a first thickness, said prosthesiscomprising a polymeric material and exposing the tubular expandableprosthesis to a solvent for a predetermined period of time toredistribute said polymeric material without substantially dissolving itto adjust a thickness of the plurality of struts to a second thickness,wherein the second thickness is greater than the first thickness.

In some embodiments, a polymer endoprosthesis includes a tubularexpandable endoprosthesis body comprising a polymeric material which hasbeen cut from a tube to form an endoprosthesis with a plurality ofstruts each having a luminal surface region, an abluminal surfaceregion, and two side surface regions extending between said luminal andabluminal surface regions, wherein the abluminal surface regions of thestruts are shaped to form concave surface regions extendingsubstantially from one side surface region to an opposite side surfaceregion; and a coating comprising at least one drug formed over at leastsome portions of the tubular expandable endoprosthesis body. The atleast one drug may coat all surface regions of the tubular expandableendoprosthesis body.

In some embodiments, a method of forming a polymer stent prosthesis witha modified shape includes the steps of forming a tubular expandableprosthesis with a plurality of struts having luminal, abluminal and sidesurface regions extending between said luminal and abluminal surfaceregions by cutting the prosthesis from a polymer tube having a firstthickness and treating the tubular expandable endoprosthesis to increasea thickness of the plurality of struts between the luminal and abluminalsurface regions while decreasing a width of the struts between the sidesurface regions by redistributing the polymer.

In some embodiments, the biodegradable stent prosthesis comprises atubular biodegradable polymeric material, said polymeric material ispatterned into a stent capable of radial expansion from a crimpeddiameter to a deployed larger diameter, wherein the stent comprises aplurality of struts joined by crowns and at least some of the crowns areconnected to adjacent crowns, wherein said patterned stent struts andcrowns, each have a luminal surface region, an abluminal surface region,and two side surface regions extending between said luminal andabluminal surface regions, wherein at least some abluminal surfaceregions (optionally substantially all abluminal surface regions) haveconcave shapes across substantially the width of said abluminal surfaceregions, and at least some side surface regions (optionallysubstantially all side surface regions) have convex shapes across thethickness of said side surface regions, wherein the stent in thedeployed diameter has sufficient strength to support a blood vessel.

In some embodiments, the biodegradable polymeric stent prosthesiscomprises a tubular biodegradable polymeric material, said polymericmaterial is patterned into a stent capable of radial expansion from acrimped diameter to a deployed larger diameter, wherein the stentcomprises a plurality of struts joined by crowns and at least some ofthe crowns are connected to adjacent crowns, wherein said patternedstent struts and crowns each have a luminal surface region, an abluminalsurface region, and two side surface regions extending between saidluminal and abluminal surface regions, wherein at least some abluminalsurface regions (optionally substantially all abluminal surface regions)have concave shapes across substantially the width of said abluminalsurface regions, and at least some side surface regions (optionallysubstantially all side surface regions) have convex shapes across thethickness of said side surface regions, wherein the stent in thedeployed diameter has sufficient strength to support a blood vessel.

In some embodiments, the biodegradable polymeric stent prosthesiscomprises a tubular biodegradable polymeric material, said polymericmaterial is patterned into a stent body capable of radial expansion froma crimped diameter to a deployed larger diameter, wherein the stent bodycomprises a plurality of struts joined by crowns and at least some ofthe crowns are connected to adjacent crowns, wherein said patternedstent structural elements each have a luminal surface region, anabluminal surface region, and two side surface regions extending betweensaid luminal and abluminal surface regions, wherein at least someabluminal surface regions (optionally substantially all abluminalsurface regions) have concave shapes across substantially the width ofsaid abluminal surface regions, and at least some side surface regions(optionally substantially all side surface regions) have convex shapesacross the thickness of said side surface regions, wherein the stentbody in the deployed diameter has sufficient strength to support a bloodvessel.

In some embodiments, the biodegradable stent prosthesis comprises atubular biodegradable polymeric material, said polymeric material has astent pattern, said stent capable of radial expansion from a crimpeddiameter to a deployed larger diameter, wherein the stent comprises aplurality of struts joined by crowns and at least some of the crowns areconnected to adjacent crowns, wherein said stent struts and crowns eachhave a luminal surface region, an abluminal surface region, and two sidesurface regions extending between said luminal and abluminal surfaceregions, wherein at least some abluminal surface regions (optionallysubstantially all abluminal surface regions) have concave shapes acrosssubstantially the width of said abluminal surface regions, and at leastsome side surface regions (optionally substantially all side surfaceregions) have convex shapes across the thickness of said side surfaceregions, wherein the stent in the deployed diameter has sufficientstrength to support a blood vessel.

In some embodiments, the biodegradable polymeric stent prosthesiscomprises a tubular biodegradable polymeric material, said polymericmaterial is patterned into a stent capable of radial expansion from acrimped diameter to a deployed larger diameter, wherein the stentcomprises a plurality of struts joined by crowns and at least some ofthe crowns are connected to adjacent crowns, wherein said patternedstent structural elements each have a luminal surface region, anabluminal surface region, and two side surface regions extending betweensaid luminal and abluminal surface regions, wherein at least someabluminal surface regions (optionally substantially all abluminalsurface regions) have concave shapes, and at least some side surfaceregions (optionally substantially all side surface regions) have convexshapes, wherein the stent in the deployed diameter has sufficientstrength to support a blood vessel.

In some embodiments, the biodegradable stent prosthesis, comprising abiodegradable polymeric material, said polymeric material is patternedinto a stent capable of expansion from a crimped diameter to a deployedlarger diameter, wherein the patterned stent comprises a plurality ofstruts, crowns, and optionally links connecting at least some adjacentcrowns, wherein said patterned stent struts, crowns, and links each havea luminal surface region, an abluminal surface region, and two sidesurface regions extending between said luminal and abluminal surfaceregions, wherein at least some abluminal surface regions (optionallysubstantially all abluminal surface regions) have concave shapes acrosssubstantially the width of said abluminal surface regions, and at leastsome side surface regions (optionally substantially all side surfaceregions) have convex shapes across the thickness of said side surfaceregions, wherein the patterned stent in the deployed diameter hassufficient strength to support a blood vessel. The polymeric materialmay be formed as a tubular body.

In some embodiments, the biodegradable stent prosthesis comprises abiodegradable polymeric material, said polymeric material is patternedinto a stent capable of expansion from a crimped diameter to a deployedlarger diameter, wherein the patterned stent comprises a plurality ofstruts, crowns, and optionally links connecting at least some adjacentcrowns, wherein said patterned stent struts, crowns, and links each havea luminal surface region, an abluminal surface region, and two sidesurface regions extending between said luminal and abluminal surfaceregions, wherein at least some abluminal surface regions (optionallysubstantially all abluminal surface regions) have concave shapes alongsubstantially the width of said abluminal surface regions, and at leastsome side surface regions (optionally substantially all side surfaceregions) have convex shapes along the thickness of said side surfaceregions, wherein the patterned stent in the deployed diameter hassufficient strength to support a blood vessel. The polymeric materialmay be formed as a tubular body.

In some embodiments, the biodegradable polymeric stent prosthesiscomprises a biodegradable polymeric material, said polymeric materialformed as a tubular body and patterned into a stent capable of expansionfrom a crimped diameter to a deployed larger diameter, wherein thepatterned stent comprises a plurality of struts joined by crowns whereinat least some adjacent crowns are connected, wherein said patternedstent struts and crowns, each have a luminal surface region, anabluminal surface region, and two side surface regions extending betweensaid luminal and abluminal surface regions, wherein at least someabluminal surface regions are (optionally substantially all abluminalsurface regions) have concave shapes across substantially the width ofsaid abluminal surface regions, and at least some side surface regions(optionally substantially all side surface regions) have convex shapesacross the thickness of said side surface regions, wherein the patternedstent in the deployed diameter has sufficient strength to support ablood vessel.

The concave abluminal surface regions and convex side surface regions,may substantially increase the surface region area along the length ofstent prosthesis, while reducing surface region porosity of the luminaland side surface regions.

The concave abluminal surface regions and convex side surface regions,may substantially increase the surface region area along the length ofstent prosthesis, while substantially maintaining surface regionporosity of the luminal and side surface regions.

The patterned stent may expand from a crimped configuration to a largerexpanded configuration substantially free from rotation of patternedstent struts, crowns, and optionally links.

The patterned stent may expand from a crimped configuration to a largerexpanded configuration having rotation of patterned stent struts,crowns, and optionally links, less than 45 degrees.

In some embodiments, the biodegradable stent prosthesis, comprises abiodegradable polymeric material, said polymeric material is patternedinto a stent capable of radial expansion from a crimped diameter to adeployed larger diameter, wherein the patterned stent comprises aplurality of struts joined by crowns wherein at least some adjacentcrowns are connected, wherein said patterned stent struts and crownseach have a luminal surface region, an abluminal surface region, and twoside surface regions extending between said luminal and abluminalsurface regions, wherein the patterned stent is treated and at leastsome abluminal surface regions (optionally substantially all abluminalsurface regions) are modified from being substantially convex shapes tobecome flat or have a concave shape across substantially the width ofsaid abluminal surface regions, and at least some side surface regions(optionally substantially all side surface regions) are modified frombeing substantially flat shapes to substantially convex shapes acrossthe thickness of said side surface regions, wherein the patterned stentin the deployed diameter has sufficient strength to support a bloodvessel.

In some embodiments, the biodegradable stent prosthesis, comprises abiodegradable polymeric material, said polymeric material is patternedinto a stent capable of expansion from a crimped diameter to a deployedlarger diameter, wherein the patterned stent comprises a plurality ofstruts joined by crowns wherein at least some adjacent crowns areconnected, wherein said patterned stent struts and crowns each have aluminal surface region, an abluminal surface region, and two sidesurface regions extending between said luminal and abluminal surfaceregions, wherein the patterned stent is treated and at least some sidesurface regions (optionally substantially all side surface regions) aremodified from being substantially flat shapes to substantially convexshapes across the thickness of said side surface regions, wherein thepatterned stent in the deployed diameter has sufficient strength tosupport a blood vessel.

The polymeric material may be formed from a tubular body.

The biodegradable prosthesis may be a polymeric biodegradableprosthesis.

In some embodiments, the biodegradable polymeric stent prosthesis,comprises a biodegradable polymeric material, said polymeric material ispatterned into a stent capable of radial expansion from a crimpeddiameter to a deployed larger diameter, wherein the patterned stentcomprises a plurality of struts joined by crowns wherein at least someadjacent crowns are connected, wherein said patterned stent struts andcrowns each have a luminal surface region, an abluminal surface region,and two side surface regions extending between said luminal andabluminal surface regions, wherein the patterned stent is treated and atleast some side surface regions (optionally substantially all sidesurface regions) are modified to substantially convex shapes across thethickness of said side surface regions, wherein the patterned stent inthe deployed diameter has sufficient strength to support a blood vessel.

In some embodiments, the biodegradable polymeric stent prosthesiscomprises a biodegradable polymeric material, said polymeric materialformed as a tubular body and patterned into a stent capable of expansionfrom a crimped diameter to a deployed larger diameter, wherein thepatterned stent comprises a plurality of struts joined by crowns whereinat least some adjacent crowns are connected, wherein said patternedstent struts and crowns each have a luminal surface region, an abluminalsurface region, and two side surface regions extending between saidluminal and abluminal surface regions, wherein the patterned stent istreated and at least some abluminal surface regions (optionallysubstantially all abluminal surface regions) are modified tosubstantially concave shapes across substantially the width of saidabluminal surface regions, and at least some side surface regions(optionally substantially all side surface regions) are modified tosubstantially convex shapes across the thickness of said side surfaceregions, wherein the patterned stent in the deployed diameter hassufficient strength to support a blood vessel.

The treatment of the stent prosthesis to modify the abluminal surfaceregions to concave shapes and the side surface regions to convex shapesmay allow the polymeric material to flow from one surface region to anadjacent surface region.

The treatment of the stent prosthesis to modify the abluminal surfaceregions to concave shapes and the side surface regions to convex shapesmay allow the polymeric material to flow from one surface region to anadjacent surface region without substantially dissolving the polymericmaterial.

The treatment of the stent prosthesis to modify the abluminal surfaceregions to concave shapes and side surface regions to convex shapes mayallow the polymeric material to flow from one surface region to anadjacent surface region, without substantially changing the stentpattern.

The treatment of the stent prosthesis to modify the abluminal surfaceregions to concave shapes and the side surface regions to convex shapesmay increase hydrophobicity of said surface regions, preferably by atleast 15%, more preferably by at least 30%, most preferably by at least50%.

The treatment of the stent prosthesis to modify the abluminal surfaceregions to concave shapes and the side surface regions to convex shapesmay allow the polymeric material to flow from one surface region to anadjacent surface region.

The treatment of the stent prosthesis to modify the abluminal surfaceregions to concave shapes and the side surface regions to convex shapesmay prevent said surface regions from rotating around their axis uponexpansion of the stent prosthesis from a crimped configuration to anexpanded larger configuration to support a blood vessel.

The treatment of the stent prosthesis to modify the abluminal surfaceregions to concave shapes and the side surface regions to convex shapesmay allow the polymeric material to flow from one surface region to anadjacent surface region, without substantially changing the weight ormass of the stent prosthesis.

The biodegradable stent prosthesis may be a polymeric biodegradablestent prosthesis. As an example, the biodegradable polymeric stentprosthesis may be substantially all comprised of polymeric material. Insome examples, the polymeric biodegradable stent prosthesis issubstantially all comprised of polymeric material and metallicradiopaque markers. In some examples, the polymeric biodegradable stentprosthesis is substantially all comprised of polymeric material andnon-polymeric radiopaque markers. In some examples, the polymericbiodegradable stent prosthesis is substantially all comprised ofpolymeric material and some non-polymeric material.

In some embodiments, the treatment of the stent prosthesis to modify theabluminal surface regions to concave shapes or to a concave shapeprovides abluminal surface regions having a concave shape, but notnecessarily identical concave shapes. Similarly, the treatment of thestent prosthesis to modify the side surface regions to convex shapes orto a convex shape provides side surface regions having a convex shapebut not necessarily identical convex shapes. The resulting shapes mayvary in radii of curvature and where on the strut, crown or link themidpoint of the curve occurs.

The polymeric degradable stent may be formed from a tubular body byextrusion, dipping, spraying, or printing, wherein the tubular body isformed and patterned at 1.1 to 1.5 times or 1.1 to 1.3 times an intendeddeployed diameter of the stent (labeled nominal diameter), and treatingthe patterned stent to form concave shapes on at least some abluminalsurface regions of the struts and crowns, and convex shapes on at leastsome side surface regions of said struts and crowns. The stentprosthesis may then be coated with a drug and polymer matrix maintainingthe concave abluminal surface regions and convex side surface regions,may then be crimped onto a delivery system, packaged, and sterilized.Optionally the tube or stent is heated at a temperature ranging between50 degrees and 150 degrees Celsius for between 1 minute and 5 hours,before patterning and/or after patterning, one or more times.

In some embodiments, the stent prosthesis formed from a substantiallycontinuous tubular body using extrusion, spraying, dipping, molding, orprinting; said tubular body has been formed into a stent comprising apattern of structural elements being radially expandable from a crimpedconfiguration to an expanded larger configuration and have sufficientstrength in the deployed configuration to support a body lumen; whereinat least some of said structural elements cross sections surface regionsextending between an abluminal surface region and a luminal surfaceregion is bulbous; and optionally wherein the thickness between theabluminal and luminal surfaces changes across the width of saidstructural elements wherein the thickest point is substantially towardsthe sides of said structural elements wherein the difference inthickness between said thickest point and thinnest point (measuredacross the abluminal and luminal surfaces and not across the bulbous orconvex side region) ranges between 1 micrometer and 15 micrometer,preferably between 2 micrometer and 10 micrometer, more preferablybetween 3 micrometer and 7 micrometer; wherein the stent structuralelements are coated with a coating comprising a drug which coatingcontours to said structural elements surface regions shapes providing athickness difference between the thickest point and the thinnest point(measured across the abluminal and luminal surfaces and not across thebulbous or convex side region) across the width of said structuralelements with the coating included ranges between 1 micrometer and 15micrometer, preferably ranges between 2 micrometer and 10 micrometer,more preferably ranges between 3 micrometer and 7 micrometer. The widthof the abluminal surface region of the structural element is generallythat portion which would contact the body lumen or blood vessel upondeployment.

When the stent structural elements are coated with a drug/polymercomposition, the drug/polymer coating has a thickness which issubstantially constant along the abluminal, luminal and side surfaces ofthe structural elements, and wherein a variation in coating thickness isless than 20%, less than 10% or less than 5% across any one or more ofthe abluminal, luminal or side surfaces.

In some examples at least some structural elements cross sections sidesurface regions extend outwardly forming a bulbous convex region;wherein said convex region has a widest and narrowest points across thethickness of said structural elements and wherein the widest point issubstantially about the center of said structural elements side surfaceregions, wherein the narrowest point is substantially about the ends(top and bottom) of said structural elements side surface region,wherein the difference between the widest and narrowest point rangesbetween 4 micrometer and 30 micrometer, preferably ranges between 5micrometer and 20 micrometer, most preferably ranges between 6micrometer and 15 micrometer. Optionally, the abluminal surface regioncross section is concave in shape with the difference between thickestand thinnest points across the width of said structural element (thethinnest point not including or considering the thickness of the bulbousor convex side region) ranges between 1 micrometer and 10 micrometers.

In some examples, at least some structural elements cross section has abulbous surface region extending between an abluminal surface region toa luminal surface region wherein the bulbous surface region comprisesportions of the luminal and abluminal surface regions and the sideregions, wherein the bulbous surface regions forms variable thicknessesand widths across the thickness and widths of said structural elements;wherein said structural elements are coated with a coating comprising adrug and a polymer, wherein said coating contours to the shape of saidsurface regions maintaining a difference in thickness and widths acrossthe thickness and widths of said structural elements cross sections. Insome examples the bulbous surface region extending between the abluminaland luminal surface regions begins at the edges of the abluminal andluminal surface regions curving up in a dogbone shape and thencontinuing into the convex curvature of the bulbous shape. It is at thiscurving up or concave portion of the bulbous shape that the greatestthickness of the structural element often occurs.

In some examples the abluminal surface has a substantially concave shapeacross the width of the at least some structural elements crosssections, wherein the concave shape is formed between two bulboussurface region on said abluminal surfaces.

In some examples the stent prosthesis structural elements have a coatingcomprising a mixture of drug and polymer, said coating is coated ontosaid structural elements wherein said coating contours to the shape ofsaid structural elements abluminal, luminal, and side surfaces.

In some examples the stent prosthesis structural elements have a coatingcomprising a mixture of drug and polymer, said coating is coated ontosaid structural elements wherein said coating contours to the shape ofsaid structural elements substantially concave abluminal surface shape,substantially concave luminal surface shape, and convex side surfaceshapes; said coating substantially maintains concave abluminal surfaceshape, concave luminal surface shape, and convex side surface shapes.

In some examples, upon application of the coating an outer surface areaof the structural elements is not substantially changed or is notchanged by more than 5%, by more than 10% or by more than 20%.

In some examples, upon application of the coating a cross sectional areaof the structural elements in not substantially changed or is notchanged by more than 5%, by more than 10% or by more than 20%.

In some examples the coating comprises a drug wherein the total drugdose ranges between 50 micrograms and 200 micrograms for an 18 mm stentprosthesis.

In some examples the surface region on at least some abluminal surfaceshave a lip or an edge across the abluminal surface region, wherein saidlip have a thickness that is different from adjacent abluminal surfaceregion, wherein the difference in thickness ranges between 2 micrometerand 10 micrometer.

In some examples, the stent prosthesis has concave luminal and/orabluminal surfaces which join convex side surfaces at a lip whichextends along at least some of the structural elements including struts,crowns and links. The lip forms a thickest portion of the structuralelement cross section. As shown in FIGS. 2A-2C and FIGS. 23 and 24, thelip may be in the shape of a wave where the concave and convex surfacesmeet. FIG. 24 shows the abluminal lips extending continuously along astrut and a connected crown.

In some examples, the stent prosthesis has a concave abluminal surfaceand two lips extending along all structural elements of the stentprosthesis.

In some examples, the stent prosthesis cross section has concave luminaland/or abluminal surfaces and convex side surfaces which form acontinuous curve across these surfaces without flat portions or withoutsubstantial flat portions. For example, the convex side surfaces providea continuous curve in the form of an arc from an abluminal lip to aluminal lip without flat portions. In some examples, the arc shape ofthe side surfaces may have a radius of curvature of about 0.02 to about0.125 or about 0.05 to about 0.075. The arc shape extends between theabluminal and luminal lips or edges.

In some examples, the convex arc shape of the two side surfaces has novisible flat surfaces under a magnification such as SEM magnification of1000×.

In some examples, the crimping of the stent prosthesis having convex arcshaped side surfaces results in a point contact or line contact betweenthe arc shaped surfaces or between the surfaces and the balloonmaterial. In some examples, the crimping of the stent prosthesis havingconvex arc shaped side surfaces results in no contact between the arcshaped surfaces. In some examples, the crimping of the stent prosthesishaving convex arc shaped side surfaces results in contact between thearc shaped surfaces and the balloon material.

In some examples, a thickness between an abluminal lip and a luminal lipforms a thickest part of the cross section, while a thickness at amidpoint or substantially a midpoint between the two luminal lips orbetween the two abluminal lips forms a thinnest part of the crosssection. A difference between the thickest and thinnest points of thecross section is at least 2%, at least 5%, at least 10%, at least 20%,or at least 30% of the maximum thickness. In some examples, a differencebetween the thickest and thinnest points of the cross section is 2% to30%, 2% to 15% or 2% to 10% of the maximum thickness.

In some examples at least some structural elements abluminal surfacesare concave across the width of said abluminal surfaces all along theentire length of said structural element as shown in FIGS. 23 and/or 24.

In some examples at least some structural elements side surfaces areconvex across the thickness of said side surfaces along the length ofsaid side surfaces as shown in FIGS. 23 and/or 24.

In some examples, at least some structural elements have a concaveabluminal surface, bulbous, dogbone, or convex side surface and a lipformed along the length of said structural element.

In some examples, the abluminal surface region has a convex shape acrossthe width of said abluminal surface, while the luminal surface regionhas a convex, concave or substantially flat shape. In some examples, theabluminal surface region has a convex shape across the width of saidabluminal surface, while the luminal surface region has concave orsubstantially flat shape and the side surfaces are substantially flat orconvex. In some examples, the abluminal surface region has a convexshape across the width of said abluminal surface with a concavedepression at about the mid-point of said abluminal surface, while theluminal surface region has a concave or substantially flat shape and theside surfaces are substantially flat or convex. In some examples bothluminal and abluminal surface regions of said structural elements aresubstantially flat. In other examples both abluminal and luminal surfaceregions are convex wherein said structural element thickest point isabout a midpoint across the abluminal and luminal surface regions, orwherein the structural element thickest point is about a midpoint acrossthe width of said structural element. In some examples of any of theprevious examples the surface region extending between luminal andabluminal surface regions is convex.

In some examples the treatment to shape the structural elements uses twoor more solvents or other chemical material in ratios ranging from 2% to95% for each solvent or other chemical material, preferably in ratiosranging from 5% to 80% for each solvent or other chemical material. Insome examples of using two or more solvents or other chemical material,at least one solvent or other chemical material is capable of dissolvingthe material substantially completely within 24 hours. In some examplesof using one or more solvents or other chemical material to treat thepolymeric material to shape it into the desired abluminal, luminal,and/or side surfaces, the treatment ranges from 0.1 seconds to 1 hour,preferably from 1 second to 1 minute, most preferably from 1 second to30 seconds. In some examples of treating using one or more solvent orother chemical material the stent polymeric material structural elementsare sprayed, dipped, or brushed with solvent or other chemical material.In some examples of treating with solvent or other chemical material thestent pattern is substantially maintained after treatment with thesolvents or other chemical material.

In a preferred example, the biodegradable stent is heat treated one ormore times after patterning and before crimping. Heat treating thebiodegradable stent after patterning and before crimping provides for atleast some of the following: increased radial strength in the deployedconfiguration. aligning the polymeric material orientation in the radialdirection, increased orientation of the polymeric material in the radialdirection, and reduced residual solvent in the stent. In one example,heat treating the biodegradable stent after patterning and aftertreatment to form the desired shape cross sectional shape for the strutsand/or crowns and before crimping provides for substantially maintainingthe stent pattern. Heat treating the biodegradable stent afterpatterning and before crimping provides for increased radial strength inthe deployed configuration. In a preferred example the stent radialstrength increases by at least 20%, in another preferred example, thestent radial strength increases in the range of 15% to 50%. The heattreatment of the biodegradable stent after patterning and beforecrimping is to a temperature ranging between Tg and Tm of the polymericmaterial, or between 70° C. and 150° C., or between 90° C. and 120° C.,typically for a time period ranging from 1 min to 10 hours, preferablyfrom 5 minutes to 5 hours, more preferably from 1 hour to 3 hours; andthen the biodegradable stent is cooled to a lower or to an ambienttemperature over a time period ranging from 1 second and 30 minutes. Thebiodegradable stent is heat treated after patterning and before crimpingwhile substantially maintaining the diameter of the patterned stent orso that the stent diameter post heat treatment is reduced by less than15% of the patterned diameter. This heat treatment substantiallymaintains the diameter of the patterned stent but there may be a slightreduction in size following the heat treatment, that is, a reduction bya magnitude ranging between 1% and 15% of the patterned stent diameteror from 0.1 mm to 1 mm of the patterned stent diameter. Thebiodegradable stent is formed at an initial diameter and patterned atthe same diameter (1.1-1.5 times the intended deployed diameter). Theheat treatment after patterning and before crimping substantiallymaintains the as-formed diameter and diameter of the stent beforepatterning. In another example, the biodegradable stent is heat treatedafter patterning and before crimping while substantially maintaining thestent initial formed diameter. The heat treatment of the biodegradablestent after patterning and before crimping does not substantially alteror deform the stent pattern or the stent pattern geometry. The heattreatment of the biodegradable stent after patterning and beforecrimping may increase crystallinity by at least 10%, preferably by atleast 15%, more preferably by at least 20%, compared to thecrystallinity of the polymeric material before heat treatment. But insome instances, the heat treatment of the biodegradable stent afterpatterning and before crimping does not substantially change thecrystallinity of the polymeric material. In one example, thebiodegradable stent is heated after patterning and before crimping whilehaving a mandrel through the patterned stent, or having a structurethrough the patterned stent, or not having any structure or mandrelthrough the stent. In another example, the biodegradable stent is heattreated after patterning and before crimping forming the desired strutand/or crown cross sectional shapes.

In another example, the biodegradable stent is treated after patterningand before crimping to form the desired strut and/or crown crosssectional shapes, and then heat treated at a temperature above the Tg ofthe polymeric material before crimping, preferably said heat treatmentis at a temperature between 70° C. and 150° C., without substantiallychanging the stent pattern or without substantially changing the stentdiameter, and then crimping said stent to a smaller configuration whilebeing heated at a temperature ranging between 40° C. and 55° C.,preferably while being heated at a temperature below the Tg of thepolymeric material. The treatment to shape the struts and/or crowns maybe one or more of chemical treatment, heating, mechanical shaping, lasershaping, or blasting. The chemical treatment may comprise contact withone or more solvents.

In another example, the biodegradable stent is heat treated afterpatterning and before crimping, said heat treatment at a temperatureabove Tg, preferably said heat treatment at a temperature between 70° C.and 150° C., without substantially changing the stent pattern or withoutsubstantially changing the stent diameter, and then crimping said stentto a smaller configuration while being heated at a temperature below Tg,preferably ranging between 40° C. and 55° C.

Before deployment, the stent is crimped to a smaller configuration in acrimper for a period of time ranging from 1 sec to 10 minutes,preferably 1 minute to 5 minutes, at a temperature about or below Tg, orwithin 5 degrees C. higher than Tg, or within 5 degrees C. lower thanTg, or ranging between 40° C. and 50° C. The stent is typically heldafter crimping at said temperatures for 1 sec to 10 minutes, preferably10 sec to 5 minutes, more preferably 20 sec to 1 minute. The stent istypically cooled after crimping for a time period ranging from 1 secondto 10 minutes, preferably 30 seconds to 5 minutes, more preferably 1minute to 3 minutes. Then the stent is sheathed after crimping on adelivery system within a time period ranging between 1 seconds to 1hour, preferably 1 second to 5 minutes.

The surface modification to the structural elements of the biodegradablestent may include heat treating the stent at greater than 15° C. aboveTg of polymer material prior to a treatment with one or more solvents;varying the treatment time in the first solvent at ambient temperaturewith agitation for a time ranging from 0.5 seconds to 5 seconds,followed by a second solvent of, for example, ethanol for time rangingfrom 0.5 seconds to 30 seconds while maintaining agitation, then heattreating the stent at a temperature above the boiling point of the firstsolvent for a time ranging from 1 minute to 5 hours while supporting thestent with a mandrel to prevent shrinkage, where in the first solventcan at least substantially dissolve the polymer and the second solventdoes not substantially dissolve the polymer. The overall treatment withthe two solvents is under conditions such that the polymeric material ofthe biodegradable stent does not substantially dissolve. The solventtreatment smoothes the surface of the stent prosthesis to remove roughedges, burrs or sharp edges.

FIGS. 26, 27 and 28 show struts examples of images of the shape of thetreated struts and/or crowns and also the strut and/or crowns as in thestent prosthesis. FIG. 29 shows an example: The concave shape at theabluminal surface of the strut cross section was 25 to 100 μm wide and 0to 25 um deep. The maximum thickness was at or near the center of thestrut cross section approximately 110 to 140 um thick and the radius ofcurvature of the convex shape mating to the abluminal surface wasapproximately 66 μm.

In one example, the side surface of the strut cross section is convex.In one example the luminal surface of the strut cross section isconcave. In one example, the luminal surface of the strut cross sectionis substantially flat. In one example, the luminal surface of the strutcross section is convex.

In one example, the radius of curvature of the convex shape of theabluminal surface region which would contact or mate with the surface ofthe vessel wall ranges from 25 micron to 100 micron, preferably between50 micron to 75 micron.

It can be appreciated that all the examples within this application areapplicable to all biodegradable materials including polymeric andmetallic materials. It can also be appreciated that all the examples offorming with a desired shape and treating to form a desired shape areapplicable to all biodegradable materials including polymeric andmetallic materials.

EXAMPLES Example 1

Biodegradable polymer stents made from polylactide based polymer weretreated with a solvent of 4 parts dichloromethane (methylene chloride)and 6 parts ethanol for 5 seconds and rinsed with ethanol for 3 seconds.Both treated and non-treated stents were then heat treated for 3 hoursat 90 deg. C. They were coated with a drug matrix coating and sterilizedby Ebeam. The stents were tested for radial strength using an Instronconnected to an iris based tester. Treated and untreated stents werechosen based on their similarity in thickness and width to show thebenefits of treatment in increasing strength for the same or similarstrut profile. As shown in Table 1, the radial strength of the treatedstents with modified structure cross section of convex sides and concaveluminal and abluminal surface region were higher by at least 15% thanthe similarly sized stents with substantially rectangular struts(non-treated).

TABLE 1 Summary of Radial Strength Radial Strut Thickness Strut WidthStrength inches micrometer In micrometer (psi) n Treated 0.0043 1100.0074 188 13.7 3 Non- 0.0046 116 0.0074 188 11.9 4 Treated

FIG. 2A shows a cross section of a stent strut after treatment. Thestent cross section before treatment had substantially rectangular lasercut struts. The stent of FIG. 2A is shown before coating with drugmatrix.

The measurements of Table 2 were taken according to the followingprocedure. However, other procedures may also be used for measurements.Deploy the stents with a balloon catheter according to standardprocedures and then dry in vacuum overnight or until there is no visiblemoisture on the stent. Support the sample with a pin gauge inside thestent prior to cutting the sample across a strut. Mount the samples onthe SEM staging using a piece of double tape and then slightly bend thestrut such that the cut edge is accessible by the SEM. Under the SEM,locate the first area of interest and then orient the view such that thecut surface is viewed “straight on” as much as possible. Scan thecross-sectioned surface with magnification, such as 1000×, 1200× or1500× magnification. A strut measurement can be taken in the middle ofthe strut using the SEM software or at a point of maximum or minimumthickness or width.

The strut after treatment has a narrower width and a slightly greaterthickness as shown in Table 2 below.

TABLE 2 Summary of Dimension Changes with Treatment Strut ThicknessStrut Width Inches micrometers Inches micrometers Before Treatment0.0032 81 0.0080 203 After Treatment 0.0043 116 0.0074 188

For the particular treatment process in this Example, the struts aftertreatment have convex side surface regions and have a slight concavityin the luminal and abluminal surface regions. The strut dimensions givenin Table 2 are maximum dimensions for the width and thickness, taken atthe widest or thickest spot on the strut. According to this example, thetreatment resulted in a 43% increase in strut thickness and a 7%decrease in strut width.

A percent shape modification treatment, or amount of change in shape,can be calculated by measuring at one cross section the minimum strutwidth, generally at the luminal or abluminal surface region of the strut(W_(min)) and the maximum strut width (W_(max)) which occurs near amidpoint between the luminal or abluminal surface region of the strutand calculating percent treatment=[1−(W_(min)-W_(max))]×100 as shown inTable 3. In some examples, the percent shape modification treatment isat least 10%, or at least 20%, or at least 30% or at least 40%.

TABLE 3 Percent Treatment Ring 1 Middle Ring Strut Strut Width WidthUnit # (in) (in) 3 × 28 mm Max Min Max Min* 1 0.0073 0.0035 0.00750.0048 2 0.0073 0.0043 0.0074 0.0045 3 0.0073 0.0044 0.0071 0.0045 40.0074 0.0042 0.0073 0.0041 5 0.0072 0.0045 0.0068 0.0031 Average 0.00730.0042 0.0072 0.0042 Low 0.0072 0.0035 0.0068 0.0031 High 0.0074 0.00450.0075 0.0048 % shape 43% modification Treatment Middle Ring Strut Ring1 Strut Width Unit # Width (in) (in) 3 × 14 mm Max Min Max Min* 1 0.00710.0045 0.0071 0.0044 2 0.0071 0.0047 0.0069 0.0046 3 0.0078 0.0048Average 0.0074 0.0047 0.0070 0.0045 Low 0.0071 0.0045 0.0069 0.0044 High0.0078 0.0048 0.0071 0.0046 % Treatment 37%

The treated stents of Example 1 were found to have no significantweight/mass change after treatment. This shows that the solvent is notremoving polymer from the stents, but is instead redistributing thepolymer material to modify the shape of the surface regions. This alsoshows that substantially all the solvent is removed from the stentsafter treatment. In this example, the difference in mass before andafter treatment is less than 1%.

TABLE 4 Mass Before and After Treatment Before shape modificationTreatment (mg) 1 5.212 2 5.309 3 5.337 Mean 5.286 After shapemodification Treatment (mg) 1 5.194 2 5.353 3 5.370 4 5.379 5 5.372 Mean5.329 % 0.81% Difference

Example 2

In some examples, samples were treated by the methods described inExample 1. For these samples, a width of the struts, crowns or links wasmeasured at a narrowest point (core) to find the minimum thickness andat the two widest portions (lip 1 and lip 2) to find two maximumthicknesses. The core was measured at about a midpoint between thelocation of lip 1 and lip 2. The maximum and minimum thicknesses arereported in Table 5 below and the cross sections are shown in FIGS. 2Band 2C. As shown in Table 5, the thickness varies between the maximumand minimum an amount of about 2% to about 10%.

TABLE 5 Variation in thickness from core to lip Min thickness AverageMax thickness Max thickness Sample Core (μm) Lip (μm) Lip 1 (μm) Lip 2(μm) FIG. 2B 91 98 101 95 FIG. 2C 94 100 99 102

Example 3

In some examples, the side and abluminal surface regions of at least aportion of the struts, crowns, links and other stent structures can beshaped by solvent dipping while maintaining a substantially flat surfaceregion on the luminal side by inserting a tight mandrel such as a Teflonrod or tube inside the stent. The stent supported tightly on the mandrelis then dipped into a first solvent for about 1 second, 2 seconds, 3seconds, or up to 20 seconds to cause the solvent to redistributepolymer material. The stent is quickly removed from the solvent when thedesired shaping is achieved. Preferably the stent is rinsed in a secondsolvent to remove materials that are adhering to the stent and to fixthe desired shape. FIG. 4 shows a cross sectional shape of a stent whichcan result from treatment by this process.

Although a tight fitting inner mandrel is described for blocking contactof the first solvent with the luminal side of the stent, other methodsof masking the luminal side can also be used to prevent shaping of theluminal surface regions of the stent. Although the luminal surfaceregion of the stent without treatment are described as substantiallyflat surface regions, it should be understood that the stent if formedfrom a tube, have surface regions with some slight curvaturecorresponding to the curvature of the tube. Substantially flat surfaceregions can occur if the structure is formed from a sheet.

Example 4

Biodegradable polymer stents made from polylactide based polymer weretreated with a solvent based stent modification process described aboveto provide a structure cross section with convex sides and concaveabluminal surface region. The modification of the stent surface regionshapes was to provide improved tracking and/or push by reducing theforce required to track or push the stent mounted on a catheter througha cylindrical body, such as a blood vessel. The reduction of track orpush force is achieved by changing the area of surface region contactbetween the modified stent shape and the vessel. On the abluminal side,the unmodified surface regions on the stent structure can act likeratchet elements as the stent is pushed through a blood vessel,especially one with calcified lesions. This may inhibit tracking throughthe vessel because the sides may get caught on the walls of the artery.

A test method was developed to characterize a force required for a stentdelivery system to cross a lesion located at the apex of a curve in atest fixture with a curved track to simulate a blood vessel.

The fixture is immersed in a water bath maintained at 37° C. and thecatheter with a mounted stent is pushed through the fixture. The pushforce is measured by the Instron attached to the catheter deliverysystem. The force is measured for units with stents with no modification(sample V) and flat side surface regions and stents with shapemodification with convex side structures (sample Y). Test results ofFIG. 16 showed a lower push force for the modified stent, indicatingbetter trackability.

Example 5

A bioresorbable stent of 6.0 mm diameter and 60 mm in length is lasercut from a tube of 200 micrometer thickness made from a copolymer ofpolylactic acid-co-glycolide. The stent is mounted on a smaller mandrelrotating around its longer axis in an enclosed refrigerated chamber andis exposed to surface region modification with dry ice blastingequipment. The sandblasting nozzle is attached to a programmable roboticarm to propel particles along the selected portions of the stent crownsand axial struts. The dry ice blasting nozzle is aimed at the luminalsurface regions to compact the treated surface region and create theconcave shape of these surface regions. The nozzle of the equipment isaimed at the corners at an angle of about 20 to about 160 degrees withrespect to the strut side surface regions to achieve compaction ofmaterial at the side surface regions at the corners to provide convexside surface regions without removing significant amounts of materialfrom other parts of the stent. As described herein, the stent can beeither tightly mounted on a mandrel or loosely mounting on a mandreldepending on the location of the surface regions to be shaped. The stentcan also be positioned inside a tube to shape at least a portion of thesurface regions on the luminal surface region of the stent.

Example 6

A bioresorbable stent of 3.5 mm diameter and 28 mm in length is lasercut from a tube of 100 micrometer thickness made from a polymer ofpolylactic acid based copolymer. A femtosecond laser is used to createconvex and concave surface region crowns on a stent. Because of theability to ablate with low energy and cut layer by layer, a lasercutting program can be set to ablate about 25 or smaller micrometerwidth slots. As shown in FIG. 17, a series of overlapping cuts are madefrom the top surface region to the edge of the stent structure 150 toachieve the desired shape on the crown, axial strut, or link. The stentstructure can be cut with off-axis control such that the axis of laserbeam and the axis of the assist gas supply nozzle on the laser such as afemtosecond laser is eccentrically oriented. This allows the laser tocut the stent material at an angle 152 rather than straight cut,eventually resulting in the convex cross section side surface regions.

FIG. 18 shows the process of the laser being used to create a concavesurface region on the luminal and/or abluminal surface regions byablating the mid-section of the crown, strut or link 150 in stepwisecuts 154 in the surface region of 150 to eventually create a concavityacross substantially the width of the crown, strut or link.

Example 7

A multi-piece metal mold is created with fine stent negative featuresusing wire EDM with the desired shaped strut features having convexsides and concave luminal and abluminal surface regions and heldtogether under high pressure with holding clamps.

The equipment used is specifically designed to mold microparts withsmall plastic shot sizes for example a 3.5 mm×28 mm stent of 13 cubicmillimeters, by utilizing high pressure of up to 100,000 psi and highspeed to achieve injection times of around 0.01 seconds, to decrease thedwell time in the mold and minimize thermal degradation of the polymer.The strut width is 200 um and thickness is 200 um.

PLA based polymer is heated in the plasticizing portion of the machine,to the melt temperature of 200° C., and fed into the mold portion of themachine by the injector plunger.

After injection the mold is cooled rapidly to freeze the molten plasticand minimize thermal degradation, and the part removed. The stentstructure has a cross section with the convex side surface regions andconcave luminal and abluminal surface regions.

Example 8

Biodegradable polymer stents made from polylactide based polymer weremeasured to determine thickness before and after treatment. The resultsare shown below in Table 6. The first stent was measured as-cut prior toany treatment. Measurement was performed by taking cross sections of thestent struts and using Micro-Vu at 315× magnification to measure thethickness. The second stent was heat treated for 3 hours at 90 deg. C.The heat treated stent has a slightly concave abluminal surface andconvex side surfaces and has a minimum thickness at substantially thecenter of the abluminal surface which is about 13% greater than theuntreated stent. Third and fourth stents were treated with a solvent of4 parts dichloromethane (methylene chloride) and 6 parts ethanol andrinsed with ethanol. Both stents were then heat treated for 3 hours at90 deg. C. The stent labeled solvent treatment A was treated for 4seconds in the solvent mixture and for 3 seconds in the ethanol rinse.The stent labeled solvent treatment B was treated for 2 seconds in thesolvent mixture and for 3 seconds in the ethanol rinse. For all stentsthe treatment of either heat alone or solvent with heat caused anincrease in minimum thickness of the struts in the range of about 10% toabout 25%. The stents tested were measured before coating with drugmatrix.

TABLE 6 Variation in thickness from core to lip Min Max thicknessAverage thickness Max thickness Sample Core (μm) Lip (μm) Lip 1 (μm) Lip2 (μm) As Cut 95.7 Heat treated 108.2 Solvent treated A 117.5 133.2130.0 136.4 Solvent Treated B 119.3 122.0 122.3 121.7

Example 9

Biodegradable polymer stents made from polylactide based polymer weremeasured to determine thickness before and after treatment. The resultsare shown below in Table 7. Measurement was performed by taking crosssections of the stent struts and using Micro-Vu at 315× magnification tomeasure the thickness. The stents were treated with a solvent of 100%tetrahydrofuran (THF) or a combination of 90% TFH and 10% ethanol andrinsed with ethanol. The stent treated with a combination of 90% TFH and10% ethanol was treated for 3 seconds and rinsed with ethanol for 5seconds. The stent was then heat treated for 3 hours at 90 deg. C. toremove substantially all of the solvent. The stent treated with asolvent of 100% TFH was treated for 1 second and rinsed with ethanol for5 seconds. The stent was then heat treated for 3 hours at 90 deg. C. toremove substantially all of the solvent. For each of the stents thetreatment caused lips to form along the struts and created a dogbone orbulbous shape of strut cross sections. The stents were measured beforecoating with drug matrix.

TABLE 7 Variation in thickness from core to lip Min Max thicknessAverage thickness Max thickness Sample Core (μm) Lip (μm) Lip 1 (μm) Lip2 (μm) THF/ethanol 90/10 105.6 106.6 105.3 108.0 treated THF Treated100.1 106.5 110.0 103.0

Example 10

An experiment was performed to measure the dimensions of the stentstructural elements including the axial length, width and thickness ofthe elements. The experiment was performed with a stent having elongatedaxial structural elements to determine the effect of heat treatment or acombination of solvent treatment and heat treatment on the dimensions ofthe stent structural elements. Measurements were taken of the strutthickness and width at approx. 1-2 mm from each end of the structuralelement and at a mid link section. The stents were treated as describedin Table 8 below and the stents were remeasured. The average percentdifference between the treated and untreated stents was calculated.

TABLE 8 Heat Treat Ony Solvent and Heat Treat Treatment duration 2 secsolvent 4 second solvent 3 hr @ 9 hr @ treatment treatment 90 C. 90 C.Heat 3 hr @ 90 C. Heat 3 hr @ 90 C. Length −3.7% −3.9% −5.8% −7.5% Width−2.3% −1.3% −9.0% −11.4% Thickness 0.1% −0.8% 12.1% 22.0%

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions;wherein at least some of the abluminal surface regions are concaveacross substantially the width of the surface, optionally at least someof the side surface regions are convex across substantially the width ofthe surface.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions;wherein at least some of the abluminal surface regions have a concaveoverall surface shape, optionally at least some of the side surfaceregions have a convex overall surface shape, where the overall shape ofa surface region is defined as the shape of a curve fitted to the actualsurface by an appropriate fitting procedure such as a least squaresfitting procedure.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions;wherein at least some of the side surface regions are convex acrosssubstantially the width of the surface and at least some of theabluminal surface regions are flat or concave across substantially thewidth of the surface.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions;wherein at least some of the side surface regions have a convex overallsurface shape and at least some of the abluminal surface regions have aconcave or flat overall surface shape, where the overall shape of asurface region is defined as the shape of a curve fitted to the actualsurface by an appropriate fitting procedure such as a least squaresfitting procedure.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions,the stent structural element having a thickness between the luminal andabluminal surface regions and a width between the side surface regions;wherein for at least some of the stent structural elements the widthvaries across the thickness.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions,the stent structural element having a thickness between the luminal andabluminal surface regions and a width between the side surface regions;wherein for at least some of the stent structural elements the widthvaries across the thickness such that the width increases in a directionaway from the luminal and abluminal surface regions.

Embodiments of the disclosure provide an biodegradable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions,the stent structural element having a thickness between the luminal andabluminal surface regions and a width between the side surface regions;wherein for at least some of the stent structural elements the widthvaries across the thickness such that a minimum width is at the luminaland abluminal surface regions.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions,the stent structural element having a thickness between the luminal andabluminal surface regions and a width between the side surface regions;wherein for at least some of the stent structural elements the thicknessvaries across the width.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions,the stent structural element having a thickness between the luminal andabluminal surface regions and a width between the side surface regions;wherein for at least some of the stent structural elements the thicknessvaries across the width such that thickness decreases in a directionaway from the side surface regions.

Embodiments of the disclosure provide an expandable stent prosthesiscomprising: a tubular expandable stent prosthesis body, said tubularexpandable stent prosthesis body comprising stent structural elementseach having a luminal surface region, an abluminal surface region andside surface regions coupling the luminal and abluminal surface regions,the stent structural element having a thickness between the luminal andabluminal surface regions and a width between the side surface regions;wherein for at least some of the stent structural elements the widthvaries across the thickness such that a minimum width is at the luminaland abluminal surface regions.

Embodiments of the disclosure provide an expandable stent prosthesisthat preferably is biodegradable.

In embodiments of the disclosure, the tubular expandable stentprosthesis body may comprise a non-braided tubular body. For example,the tubular expandable stent prosthesis body may comprise a patternedtubular body. The patterned tubular body may be patterned by cutting oretching, for example by use of a laser. As examples the tube may beformed by extrusion, spraying, dipping or molding. The tubularexpandable stent prosthesis body may be formed as a tube or from a flatsheet which may be patterned before or after being formed into acylinder to form the tubular body. Any of these tubular bodies may bepre-formed with the above-described surface shapes or may be modifiedafter formation to provide the above-described surface shapes. Where atubular body is formed from a flat sheet then the flat sheet may bepre-formed with the above-described surface shapes or may be modifiedafter formation to provide the above-described surface shapes.

In embodiments, concave abluminal surface regions can provide benefitsin drug coating and in drug delivery and benefits in embedding the stentprosthesis into the vessel wall. In embodiments, a reduction of trackingor push force required to track or push a stent mounted on a catheterthrough a cylindrical body, such as a blood vessel, may be achievedbecause of the change of the area of contact between the stentprosthesis and the vessel wall resulting from the surface regionshaping. In embodiments, a lower push force may be required for stentprostheses with convex side surface regions than for stent prostheseswith flat side surface regions, providing better trackability.

In some examples, the stent prosthesis is formed as a tubular body byextrusion, dipping, molding or printing and then patterned into a stent.In some examples the stent prosthesis is formed as a sheet, wherein thesheet is rolled to form a tubular body wherein the sheet is patternedinto a stent before or after forming into a tubular body. The rolledsheet edges are affixed or joined together to form a tubular body bytreatment such as using heating, chemical bonding, ultrasound bonding,laser bonding or other means. In some examples the stent prosthesis isformed as a sheet, wherein the sheet is patterned prior to rolling thepatterned stent into a tubular patterned stent using the methodsdescribed previously. In some examples, the stent prosthesis is formedas a tubular pattered body, wherein the patterning and forming of thetubular body take place concurrently, such as the example of 3-Dprinting. In some examples, the stent prosthesis is formed as a threedimensional structure or body and then patterned into a stent. In someexamples, the stent prosthesis is formed as a substantially tubular bodyand then patterned into a stent. In any of the above examples thestructural elements are formed with the desired shape or treated to formthe desired shape as described herein.

Example 11

A PLLA based polymeric tubular material was formed and patterned using alaser into a stent. The stent was then heat treated at 90° C. for 3hours. The stent was coated with a drug/polymer matrix, crimped onto acatheter while being heated at a temperature at about 45° C., packaged,and sterilized. A control group was also made using the same steps andparameters without heat treating the stent after patterning and beforecrimping (without heating the stent to 90° C. for 3 hours). The unitswere then tested for radial strength (iris compression test). Theresulting radial strength increased for the heat treated group.

TABLE 9 Radial Strength Test Arm (n = 3) (psi) 3.0 × 14 mm Control 15.63.0 × 14 mm heat treatment 18.1 post patterning and before crimping

Example 12

A PLLA based polymeric tubular material is formed and patterned using alaser into a stent. The stent is then treated by exposing it to asolvent mixture of DCM and Ethanol for 0.1-1.5 second. The stent is thenexposed to ethanol for 1-5 seconds. The scaffold is then heat treated at90° C. for 3 hours. The stent is coated with a drug/polymer matrix,crimped onto a catheter while being heated at a temperature below 55°C., packaged, and sterilized. The biodegradable stent is deployed fromthe crimped configuration to the deployed expanded configuration whereinthe stent in the deployed configuration has a strength sufficient tosupport a body lumen.

Throughout the specification, including the claims, where the contextpermits, the term “comprising” and variants thereof such as “comprises”or “comprising” are to be interpreted as including the stated integer orintegers without necessarily excluding any other integers.

The Disclosure of this Application Also Includes the Following NumberedClauses:

1. An expandable biodegradable stent prosthesis comprising:

a tubular expandable stent prosthesis body comprising a biodegradablematerial, said expandable stent prosthesis body comprising stentstructural elements having luminal and abluminal surface regions;wherein at least some of the abluminal surface regions have a concaveshape across substantially the width of said surface regions.

In embodiments of the disclosure, a concave abluminal surface regionminimizes or at least reduces the possibility of slippage of the stentprosthesis when expanded to a deployed configuration, such that thestent structural elements hug the vessel wall or the plaque area better.

In embodiments of the disclosure, concave abluminal surface regions mayprevent or reduce rotating of stent structural elements during crimpingand/or during expansion.

In embodiments of the disclosure, concave luminal and/or abluminalsurface regions may also provide improved directionality of drugdelivery to the lumen or vessel wall.

2. The expandable biodegradable stent prosthesis of clause 1, whereinsaid stent structural elements each have side surface regions extendingbetween the luminal and abluminal surface regions; and wherein at leastsome of the side surface regions have a convex shape acrosssubstantially the thickness of said stent structural elements.

3. The expandable biodegradable stent prosthesis of clause 1 or 2,wherein substantially all of the side surface regions have a convexshape across substantially the thickness of said side surface regions.

In embodiments of the disclosure, concave abluminal surface regions andconvex side surface regions, may increase the surface region area alongthe length of stent prosthesis, while reducing or maintaining surfaceregion porosity of the luminal and side surface regions.

4. The expandable biodegradable stent prosthesis of clause 1, whereinsaid stent structural elements each have side surface regions extendingbetween the luminal and abluminal surface regions; and wherein at leastsome of the side surface regions have a concave shape acrosssubstantially the thickness of said stent structural elements.

5. The expandable biodegradable stent prosthesis of clause 4, whereinsubstantially all of the side surface regions have a concave shapeacross substantially the thickness of said side surface regions.

6. The expandable biodegradable stent prosthesis of any of clauses 1 to5, wherein substantially all of the abluminal surface regions have aconcave shape across substantially their width.

7. The expandable biodegradable stent prosthesis of any of clauses 1 to6, wherein at least some of the luminal surface regions have a concaveshape across substantially the width of said surface regions.

8. The expandable biodegradable stent prosthesis of clause 7, whereinsubstantially all of the luminal surface regions have a concave shapeacross substantially their width.

9. An expandable biodegradable stent prosthesis comprising:

a tubular expandable stent prosthesis body, said expandable stentprosthesis body comprising stent structural elements each having asurface with a luminal surface region, an abluminal surface region,coupling portions coupling the abluminal and luminal surface regions,and a thickness between said luminal and abluminal surface regions;wherein at least a part of at least some of the coupling portions isbulbous.

10. The expandable stent prosthesis of clause 9, wherein the abluminalsurface region is flat.

11. The expandable stent prosthesis of clause 9, wherein the abluminalsurface region is concave.

12. The expandable stent prosthesis of clause 9, 10 or 11, wherein theluminal surface region is flat.

13. The expandable stent prosthesis of clause 9, 10 or 11, wherein theluminal surface region is flat.

14. The expandable stent prosthesis of any of clauses 9 to 13, whereinthe surface has two side surface regions each coupling the abluminal andluminal surface regions and the side surface regions comprise bulbouscoupling portions.

15. The expandable stent prosthesis of any of clauses 9 to 13, whereinthe surface has two side surface regions each coupling the abluminal andluminal surface regions and there are two bulbous coupling portions eachdefined by the abluminal surface region and a respective one of the sidesurface regions.

16. The expandable stent prosthesis of any of clauses 9 to 13, whereinthe surface has two side surface regions each coupling the abluminal andluminal surface regions and there are two bulbous coupling portions eachdefined by the luminal surface region and a respective one of the sidesurface regions.

17. The expandable stent prosthesis of any of clauses 9 to 13, whereinthe surface has two side surface regions each coupling the abluminal andluminal surface regions and there are four bulbous coupling portions twodefined by the luminal surface region and the side surface regions andtwo defined by the luminal surface region and the side surface regions.

18. The expandable stent prosthesis of clause 9, wherein the surface hasa dogbone or dumbbell shape with two opposed end bulbous couplingportions.

19. The expandable stent prosthesis of clause 9, wherein the surface hastwo side surface regions each coupling the abluminal and luminal surfaceregions and there are two bulbous coupling portions each defined by theabluminal surface region and a respective one of the side surfaceregions, wherein the abluminal surface region has a concave portion.

20. The expandable stent prosthesis of clause 9, wherein the surface hastwo side surface regions each coupling the abluminal and luminal surfaceregions and there are two bulbous coupling portions each defined by theabluminal surface region and a respective one of the side surfaceregions, wherein the abluminal surface region has a concave portion, theside regions are flat and the luminal surface region is flat or convex.

21. The expandable prosthesis of any of clauses 2 to 8, wherein thestent structural elements each have two side surface regions extendingbetween the luminal and abluminal surface regions.

22. The expandable stent prosthesis of any of clauses 1 to 21, whereinthe stent structural elements comprise struts and crowns.

23. The expandable stent prosthesis of clause 22, wherein the stentprosthesis body comprises expandable rings, each ring is composed ofstruts joined by crowns, and each ring is connected to an adjacent ringby at least one link.

24. The expandable stent prosthesis of any of clauses 1 to 23 whereinsaid surface region shape is formed by treating the expandable stentprosthesis.

25. The expandable stent prosthesis of clause 24, wherein the treatmentincludes shaping by application of a solvent by at least one of dipping,spraying, or contact with a solvent vapor.

26. The expandable stent prosthesis of clause 24 or 25, wherein thetreatment includes shaping by tumbling, agitating, deburring, scraping,media blasting, laser treatment or heat treatment.

27. The expandable stent prosthesis of clause 24, 25 or 26, wherein aweight of the expandable stent prosthesis after treatment issubstantially the same as before treatment.

28. The expandable stent prosthesis of any of clauses 24 to 27, whereinthe treatment does not significantly dissolve the polymeric materialfrom which said prosthesis is formed.

29. The expandable stent prosthesis of any of clauses 24 to 28 whereinthe treatment shifts material from a surface region of a said stentstructural element to an immediately adjacent surface region of a saidstent structural element without a substantial change in body weight ofsaid expandable stent prosthesis.

30. The expandable stent prosthesis of any of clauses 24 to 29, saidbody has been treated to adjust a thickness of stent structural elementsfrom a first thickness before treatment to a second thickness aftertreatment, wherein the second thickness is greater than the firstthickness.

31. The expandable stent prosthesis of any of clauses 24 to 30, whereinthe treatment causes a thickness of stent structural elements betweenthe luminal and abluminal surface regions to increase while a width ofthe stent structural elements between the side surface regions remainssubstantially the same.

32. The expandable stent prosthesis of any of clauses 24 to 31, whereinthe treatment causes a thickness of stent structural elements betweenthe luminal and abluminal surface regions to increase while decreasing aminimum width of the stent structural elements between the side surfaceregions by redistributing the biodegradable material.

33. The expandable stent prosthesis of any of clauses 24 to 32, whereinthe treatment comprises exposing the expandable stent prosthesis to asolvent for a predetermined period of time.

34. The expandable stent prosthesis of any of clauses 1 to 33, whereinthe expandable stent prosthesis body has been patterned from a tube by alaser.

35. The expandable stent prosthesis of any of clauses 1 to 34, furthercomprising a coating formed over at least some portions of theexpandable stent prosthesis body.

36. The expandable stent prosthesis of clause 35, wherein surface regionshape is retained after coating.

37. The expandable stent prosthesis of clause 35 or 36 wherein thecoating comprises a drug.

38. The expandable stent prosthesis of any of clauses 1 to 37, whereinthe biodegradable material comprises biodegradable polymeric material.

39. The expandable stent prosthesis of clause 38, wherein thebiodegradable polymeric material comprises at least one materialselected from the group consisting of lactides, poly-DL-Lactide,polylactide-co-gycolide, polylactide-co-polycaprolactone, poly(L-lactide-co-trimethylene carbonate), polytrimethylene carbonate,polyhydroxybutyrate, polyhydroxyvalerate, poly orthoesters, polyanhydrides, polylactide, polyglycolides, polycaprolactone,polyiminocarbonates and copolymers thereof.

40. The expandable stent prosthesis of clause 38 or 39, wherein thebiodegradable polymeric material of said expandable stent prosthesisbody comprises at least two biodegradable polymers.

41. The expandable prosthesis of clause 38, 39 or 40, wherein thebiodegradable polymeric material has an elastic modulus of at least 0.35GPa.

42. The expandable stent prosthesis of clause 38 or 39, wherein thebiodegradable polymeric material comprises one or more of polymers andcopolymers.

43. The expandable stent prosthesis of any of clauses 38 to 42, whereinthe biodegradable polymeric material has a molecular weight ranging from100 KDa to 1000 KDa.

44. The expandable stent prosthesis of any of clauses 1 to 43, whereinthe prosthesis is balloon expandable.

45. An expandable biodegradable stent prosthesis comprising:

a tubular expandable stent prosthesis body, which may comprise abiodegradable material, such as a biodegradable polymeric material,wherein the stent comprises a plurality of stent structural elements,wherein said structural elements each have a luminal surface region, anabluminal surface region, and two side surface regions extending betweenthe luminal and abluminal surface regions; and wherein at least some ofthe side surface regions have a convex shape.

In some examples, the surface region area over which the tensile andcompressive stresses are distributed during bending of a stentstructural element is increased due to the convex side surface regionsand this leads to increased radial strength of the stent prosthesis.

In some examples, convex side surface regions enable greater contactthan square or rectangular flat surface regions between balloon materialof the delivery system and the stent prosthesis. For example, in aprocess of crimping the stent prosthesis onto a balloon, there may be anincreased surface region area of contact between the stent structuralelement with convex side regions and a flap of the balloon than with theflat side surface regions which may enable improved stent retention on aballoon catheter in a crimped configuration. Convex side surface regionscan also improve crimping of the stent prosthesis because convex sidesurface regions are more resistant to overlapping or twisting which mayoccur with flat rectangular surface regions during expansion and/orduring crimping.

In some examples, convex side surface regions can also improveflexibility of the stent prosthesis. For example, a stent structuralelement stent with convex side surface regions may be able to bend inmore directions than to a stent structural element with flat surfaceregions providing a more flexible and deliverable stent prosthesis.

In some examples, when stent structural elements are coated with a drugfor delivery to a lumen, convex side surface regions can provide for amore uniform drug coating and thus can release drug from a substantiallymore uniform surface region than a square or rectangular strut.

46. The expandable biodegradable stent prosthesis of clause 45, whereinat least some of the abluminal surface regions have a concave shape orare flat across substantially the width of said abluminal surfaceregions.

47. The expandable biodegradable stent prosthesis of clause 45 or 46,wherein substantially all of the side surface regions have a convexshape across substantially the thickness of said side surface regions.

48. The expandable biodegradable stent prosthesis of clause 45, 46 or47, wherein said prosthesis has been treated by contact with a solventto redistribute said biodegradable material to provide said surfaceregion shape.

49. The expandable biodegradable stent prosthesis of clause 45, 46, 47or 48, wherein said prosthesis has been treated by contact with asolvent to redistribute said biodegradable material to provide anincreased thickness of said side surface regions and decreased width ofsaid abluminal and luminal surface regions.

50. The expandable biodegradable stent prosthesis of any of clauses 45to 49, wherein substantially all of the abluminal surface regions have aconcave shape across substantially their width.

51. The expandable biodegradable stent prosthesis of any of clauses 45to 50, wherein at least some of the luminal surface regions have aconcave shape across substantially the width of said surface regions.

52. The expandable biodegradable stent prosthesis of any of clauses 45to 50, wherein at least some of the luminal surface regions are flatacross substantially the width of said surface regions.

53. The expandable biodegradable stent prosthesis of any of clauses 45to 50, wherein at least some of the luminal surface regions have aconcave shape across substantially the width of said surface regions.

54. The expandable stent prosthesis of any of clauses 45 to 53, whereinthe stent structural elements comprise struts and crowns.

55. The expandable stent prosthesis of clause 54, wherein the stentprosthesis body comprises expandable rings, each ring is composed ofstruts joined by crowns, and each ring is connected to an adjacent ringby at least one link.

56. The expandable stent prosthesis of any of clauses 45 to 55 whereinsaid surface region shape is formed by treating the expandable stentprosthesis.

57. The expandable stent prosthesis of clause 56, wherein the treatmentincludes shaping by application of a solvent by at least one of dipping,spraying, or contact with a solvent vapor.

58. The expandable stent prosthesis of clause 46 or 47, wherein thetreatment includes shaping by tumbling, agitating, deburring, scraping,media blasting, laser treatment or heat treatment.

59. The expandable stent prosthesis of clause 56, 57 or 58, wherein aweight of the expandable stent prosthesis after treatment issubstantially the same as before treatment.

60. The expandable stent prosthesis of any of clauses 45 to 59, whereinthe treatment does not significantly dissolve the polymeric materialfrom which said prosthesis is formed.

61. The expandable stent prosthesis of any of clauses 45 to 60 whereinthe treatment shifts material from a surface region of a said stentstructural element to an immediately adjacent surface region of a saidstent structural element without a substantial change in body weight ofsaid expandable stent prosthesis.

62. The expandable stent prosthesis of any of clauses 45 to 61, saidbody has been treated to adjust a thickness of stent structural elementsfrom a first thickness before treatment to a second thickness aftertreatment, wherein the second thickness is greater than the firstthickness.

63. The expandable stent prosthesis of any of clauses 45 to 62, whereinthe treatment causes a thickness of stent structural elements betweenthe luminal and abluminal surface regions to increase while a width ofthe stent structural elements between the side surface regions remainssubstantially the same.

64. The expandable stent prosthesis of any of clauses 45 to 62, whereinthe treatment causes a thickness of stent structural elements betweenthe luminal and abluminal surface regions to increase while decreasing aminimum width of the stent structural elements between the side surfaceregions by redistributing the biodegradable material.

65. The expandable stent prosthesis of any of clauses 45 to 64, whereinthe treatment comprises exposing the expandable stent prosthesis to asolvent for a predetermined period of time.

66. The expandable stent prosthesis of any of clauses 45 to 65, whereinthe expandable stent prosthesis body has been patterned from a tube by alaser.

67. The expandable stent prosthesis of any of clauses 45 to 66, furthercomprising a coating formed over at least some portions of theexpandable stent prosthesis body.

68. The expandable stent prosthesis of clause 67, wherein surface regionshape is retained after coating.

69. The expandable stent prosthesis of clause 67 or 68 wherein thecoating comprises a drug.

70. The expandable stent prosthesis of any of clauses 45 to 69, whereinthe biodegradable material comprises biodegradable polymeric material.

71. The expandable stent prosthesis of clause 70, wherein thebiodegradable polymeric material comprises at least one materialselected from the group consisting of lactides, poly-DL-Lactide,polylactide-co-gycolide, polylactide-co-polycaprolactone, poly(L-lactide-co-trimethylene carbonate), polytrimethylene carbonate,polyhydroxybutyrate, polyhydroxyvalerate, poly orthoesters, polyanhydrides, polylactide, polyglycolides, polycaprolactone,polyiminocarbonates and copolymers thereof.

72. The expandable stent prosthesis of clause 70 or 71, wherein thebiodegradable polymeric material of said expandable stent prosthesisbody comprises at least two biodegradable polymers.

73. The expandable prosthesis of clause 70, 71 or 72, wherein thebiodegradable polymeric material has an elastic modulus of at least 0.35GPa.

74. The expandable stent prosthesis of clause 70 or 73, wherein thebiodegradable polymeric material comprises one or more of polymers andcopolymers.

75. The expandable stent prosthesis of any of clauses 70 to 74, whereinthe biodegradable polymeric material has a molecular weight ranging from100 KDa to 1000 KDa.

76. The expandable stent prosthesis of any of clauses 45 to 75, whereinthe prosthesis is balloon expandable.

77. An expandable biodegradable stent prosthesis comprising:

a tubular expandable stent prosthesis body comprising a biodegradablepolymeric material, said expandable stent prosthesis body comprisingstent structural elements each having a luminal surface region and anabluminal surface region and a thickness between said luminal andabluminal surfaces; wherein a side surface region extending between theabluminal surface region and the luminal surface region of at least somestructural elements is bulbous.

78. The expandable prosthesis of clause 77, wherein two side surfaceregions extending between the luminal and abluminal surface regions ofat least some stent structural elements are bulbous.

79. The expandable stent prosthesis of clause 78, wherein at least someof the abluminal surface regions are concave between the two bulbousside surface regions.

80. The expandable prosthesis of clause 77, 78 or 79, wherein a width ofthe stent structural elements between the side surface regions isgreater at about the mid-point between said abluminal and luminalsurface regions.

81. The expandable stent prosthesis of any of clauses 77 to 80, whereinthe stent structural elements comprise expandable rings, each ringcomprising struts joined by crowns, and each ring is connected to anadjacent ring by at least one link.

82. The expandable stent prosthesis of any of clauses 77 to 81, whereinthe stent structural elements comprise struts joined by crowns.

83. The expandable prosthesis of any of clauses 77 to 82, wherein atleast some of said stent structural elements are oval in cross section.

84. The expandable prosthesis of any of clauses 77 to 83, wherein thebiodegradable polymeric material of said expandable stent prosthesisbody comprises at least two biodegradable polymers.

85. The expandable prosthesis of any of clauses 77 to 84, furthercomprising at least some of the abluminal surface regions being concaveor flat across substantially the width of said surface regions.

86. The expandable prosthesis of any of clauses 77 to 85, wherein theexpandable stent prosthesis body has been patterned from a tube by alaser.

87. The expandable prosthesis of clause 86, wherein the expandableprosthesis body is formed from a substantially continuous body free fromdiscontinuities before patterning.

88. The expandable prosthesis of any of clauses 77 to 87, wherein thestent structural elements have been treated to form the bulbous region.

89. The expandable stent prosthesis of clause 85, wherein the expandablestent prosthesis body has been patterned from a tube by a laser andwherein the stent structural elements have been treated to form saidconcave or flat abluminal surface regions and bulbous side surfaceregions.

90. The expandable stent prosthesis of clause 88 or 89, wherein thetreatment includes shaping by application of a solvent by at least oneof dipping, spraying, or contact with a solvent vapor.

91. The expandable stent prosthesis of clause 88 or 89, wherein thetreatment includes shaping by tumbling, agitating, deburring, scraping,media blasting, laser treatment or heat treatment.

92. The expandable stent prosthesis of any of clauses 77 to 91, furthercomprising a coating of at least one drug formed over at least someportions of the expandable stent prosthesis body.

93. The expandable stent prosthesis of any of clauses 77 to 92, furthercomprising a coating over the expandable stent prosthesis body, saidbulbous regions of said stent structural elements remainingsubstantially bulbous after coating.

94. The expandable stent prosthesis of clause 88 or 89 or any clausedependent upon clause 88 or 89, wherein a weight of the expandable stentprosthesis after treatment is substantially the same as beforetreatment.

95. The expandable prosthesis of any of clauses 77 to 94, wherein thebiodegradable polymeric material has an elastic modulus of at least 0.35GPa.

96. The expandable stent prosthesis any of clauses 77 to 95, wherein thebiodegradable polymeric material comprises one or more of polymers andcopolymers.

97. The expandable stent prosthesis of any of clauses 77 to 96, whereinthe prosthesis is expandable from a crimped diameter to a deployedlarger diameter at body temperature.

98. The expandable stent prosthesis of clause 81 or any clause dependentthereon, wherein the prosthesis is expandable from a crimped diameter toa deployed diameter at body temperature without substantial rotation ofat least one of the struts, crowns or links about their axis.

99. The expandable stent prosthesis of any of clauses 77 to 98, whereinthe biodegradable polymeric material comprises at least one materialselected from the group consisting of lactides, poly-DL-Lactide,polylactide-co-gycolide, polylactide-co-polycaprolactone, poly(L-lactide-co-trimethylene carbonate), polytrimethylene carbonate,polyhydroxybutyrate, polyhydroxyvalerate, poly orthoesters, polyanhydrides, polylactide, polyglycolides, polycaprolactone,polyiminocarbonates and copolymers thereof.

100. The expandable stent prosthesis of any of clauses 77 to 99, whereinthe prosthesis is balloon expandable.

101. The expandable stent prosthesis of clause 88 or 89 or any clausedependent upon clause 88 or 89, wherein the treatment does not dissolvethe polymeric material from which said prosthesis is formed.

102. The expandable stent prosthesis of clause 82 or any clausedependent thereon, wherein said prosthesis has been treated to shiftmaterial from the surface region of some struts and/or crowns to animmediately adjacent surface region of said strut or crown without asubstantial change in body weight of said expandable stent prosthesis.

103. The expandable stent prosthesis of any of clauses 77 to 102,wherein biodegradable polymeric material has a molecular weight rangingfrom 100 KDa to 1000 KDa.

104. The expandable stent prosthesis of any of clauses 77 to 103, saidbody has been treated to adjust a thickness of the plurality of stentstructural elements from a first thickness before treatment to a secondthickness after treatment, wherein the second thickness is greater thanthe first thickness.

105. The expandable stent prosthesis of clause 80 or any clausedependent thereon, wherein said body has been treated to cause athickness of a plurality of stent structural elements between theluminal and abluminal surface regions to increase while a width of thestent structural elements between the side surface regions remainssubstantially the same.

106. The expandable stent of clause 88 or 89 or any clause dependentupon clause 88 or 89, wherein the treatment comprises exposing theexpandable prosthesis to a solvent for a predetermined period of timeprovide substantially at least some bulbous side surface regions and atleast some concave or flat abluminal surface regions of said stentstructural elements.

107. The expandable stent prosthesis of clause 88 or 89 or any clausedependent upon clause 88 or 89, wherein the treatment causes a thicknessof the plurality of stent structural elements between the luminal andabluminal surface regions to increase while decreasing a minimum widthof the stent structural elements between the side surface regions byredistributing the polymeric material.

108. The expandable stent prosthesis of any of clauses 77 to 107,wherein said prosthesis has been treated by contact with a solvent toredistribute said polymeric material to provide an increased thicknessof said stent structural elements and a decreased width of said stentstructural elements.

109. An expandable biodegradable stent prosthesis comprising:

an expandable stent prosthesis body comprising a biodegradable polymericmaterial, wherein the stent comprises a plurality of stent structuralelements, wherein said stent structural elements each have a luminalsurface region, an abluminal surface region, and two side surfaceregions extending between the luminal and abluminal surface regions; andwherein at least some of the stent structural elements have a bulbousshape coupling said abluminal and said luminal surface regions to form adogbone shaped cross section.

110. The expandable stent prosthesis of clause 109, wherein some of saidbulbous shaped regions have a convex shape and have a flat portion.

111. The expandable biodegradable stent prosthesis of clause 109 or 110,wherein said prosthesis has been treated by contact with a solvent toredistribute said polymeric material to provide said shapes.

112. The expandable biodegradable stent prosthesis of clause 109 or 110,wherein said prosthesis has been treated by contact with a solvent toredistribute said polymeric material to provide an increased thicknessof said side surface regions and decreased width of said abluminal andluminal surface regions.

113. The expandable stent prosthesis of any of clauses 77 to 112,wherein said stent prosthesis further comprises radiopaque markers.

114. The expandable stent prosthesis of any of clauses 77 to 113,wherein the stent further comprises metallic material.

115. An expandable biodegradable stent prosthesis comprising:

a tubular expandable stent prosthesis body comprising a biodegradablepolymeric material, said expandable stent prosthesis body comprisingstent structural elements each having a luminal surface and an abluminalsurface and a thickness between said luminal and abluminal surfaces;wherein the thickness varies across the width of at least some of thestructural elements.

116. The expandable stent prosthesis of clause 115, wherein saidthickness of at least some stent structural elements is greater at anedge of said abluminal surface region than the thickness near the middleof said abluminal surface region of said structural elements.

117. The expandable stent prosthesis of clause 115, wherein saidthickness of at least some stent structural elements is smaller at anedge of said abluminal surface region than the thickness near the middleof said abluminal surface region of said structural elements.

118. The expandable prosthesis of clause 115, 116 or 117, wherein thestent structural elements have two side surface regions extendingbetween the luminal and abluminal surface regions, wherein at least someof the side surface regions are convex.

119. The expandable prosthesis of clause 118, wherein a width of thestent structural elements between the side surface regions also variesacross the thickness of at least some stent structural elements.

120. The expandable stent prosthesis of any preceding clause, wherein atleast some abluminal surface regions and/or at least some luminalsurface regions have a lip.

121. The expandable stent prosthesis of clause 120, wherein a point onsaid lip has a thickness that is different from the adjacent abluminalsurface region, for example wherein the difference in thickness rangesbetween 2 micrometer and 10 micrometer.

122. The expandable stent prosthesis of any preceding clause, whereinconcave luminal and/or abluminal surface regions join convex sidesurface regions at a lip which extends along at least some of thestructural elements.

123. The expandable stent prosthesis of clause 122, wherein the lipforms a thickest point of the structural element cross section.

124. The expandable stent prosthesis of any of clauses 120 to 123,wherein the lip is in the shape of a wave where the surface regionsmeet.

125. The expandable stent prosthesis of any of clauses 120 to 124,wherein the lips extend continuously along a strut and a connected crownof the expandable stent prosthesis.

126. The expandable stent prosthesis of any of clauses 120 to 125,wherein the stent prosthesis cross section has concave luminal and/orabluminal surface regions and convex side surface regions which form acontinuous curve across these surface, for example, the convex sidesurfaces provide a continuous curve in the form of an arc which extendsbetween abluminal and luminal lips.

127. The expandable stent prosthesis of any of clauses 120 to 126,wherein at least some abluminal surface regions and at least someluminal surface regions have a lip and a thickness between an abluminallip and a luminal lip forms a thickest part of the cross section, whilea thickness at a core or substantially a midpoint between the abluminallip and the luminal lip or between the abluminal lips forms a thinnestpart of the cross section, for example a difference between the thickestand thinnest portions of the cross section may be at least 2%, at least5%, at least 10%, at least 20%, or at least 30% of the maximumthickness.

128. The expandable stent prosthesis of any of the preceding clauses,wherein upon application of a coating an outer surface area of thestructural elements is not substantially changed or is not changed bymore than 5%, by more than 10% or by more than 20%.

129. The expandable stent prosthesis of any of the preceding clauses,wherein upon application of the coating a cross sectional area of thestructural elements in not substantially changed or is not changed bymore than 5%, by more than 10% or by more than 20%.

130. A biodegradable stent prosthesis comprising a polymeric materialwherein the stent prosthesis has been formed from a tubular body havingan initial diameter using extrusion, spraying, dipping, molding, orprinting, and wherein the tubular body has been patterned into a stentwith a patterned diameter, said stent comprising structural elementswhich have abluminal, luminal and side surface regions, said structuralelements comprising struts joined by crowns wherein said struts andcrowns have an initial thickness and an initial width, wherein saidstructural elements have been treated to change the thickness or thewidth of at least some structural elements, said stent prosthesis beingexpandable from a crimped configuration to an expanded largerconfiguration and having sufficient strength to support a body lumen,said stent prosthesis is expandable to the larger configuration withoutfracture.

131. The biodegradable stent prosthesis of clause 130, wherein thetubular body has been exposed to an additional treatment beforepatterning wherein the additional treatment comprises at least one ormore of heating, cooling, pressurizing the polymeric material, orchemically treating the polymeric material.

132. The biodegradable stent prosthesis of clause 130 and 131, whereinthe treatment is after patterning and comprises one or more of chemicaltreatment, heating, mechanical shaping, laser shaping or blasting.

133. The biodegradable stent prosthesis of any of clauses 130 to 132,wherein the polymeric material has been treated during patterningwherein the treatment comprises at least one or more of heating, solventtreatment, mechanical shaping, laser shaping or blasting.

134. The biodegradable stent prosthesis of any of clauses 130 to 133,wherein the treatment to change the thickness or width is afterpatterning.

135. The biodegradable stent prosthesis of any of clauses 130 to 134,wherein the thickness is larger after treatment.

136. The biodegradable stent prosthesis of any of clauses 130 to 135,wherein the thickness is increased at least in one region across thewidth of said structural elements.

137. The biodegradable stent prosthesis of any of clauses 130 to 136,wherein the thickness is increased at least in at least two regionsacross the width of said structural elements.

138. The biodegradable stent prosthesis of any of clauses 130 to 137,wherein the thickness increase is variable across the width of saidstructural elements.

139. The biodegradable stent prosthesis of any of clauses 130 to 138,wherein the thickness of said structural elements is greater adjacentthe sides of said structural elements.

140. The biodegradable stent prosthesis of any of clauses 130 to 139,wherein the thickness is smallest near a midpoint between the sides ofsaid structural elements.

141. The biodegradable stent prosthesis of any of clauses 130 to 140,wherein the thickness changes after treatment by from 2 micrometer to 35micrometer, preferably between 3 micrometer and 20 micrometer, mostpreferably between 4 micrometer and 10 micrometer.

142. The biodegradable stent prosthesis of any of clauses 130 to 141,wherein the structural elements width changes after treatment.

143. The biodegradable stent prosthesis of any of clauses 130 to 142,wherein the width of said structural elements becomes smaller aftertreatment.

144. The biodegradable stent prosthesis of any of clauses 130 to 143,wherein the width changes across said structural elements.

145. The biodegradable stent prosthesis of any of clauses 130 to 144,wherein the width of said structural elements is greatest at about thecenter of said structural elements.

146. The biodegradable stent prosthesis of any of clauses 130 to 145,wherein the width changes after treatment by from 2 micrometer to 35micrometer, preferably between 3 micrometer and 20 micrometer, mostpreferably between 4 micrometer and 10 micrometer.

147. The biodegradable stent prosthesis of any of clauses 130 to 146,wherein the structural elements have an initial shape, wherein thetreatment changes the shape of said structural elements.

148. The biodegradable stent prosthesis of any of clauses 130 to 147,wherein the treatment changes the shape of said structural elements byforming a protruding bulbous region between the luminal and abluminalsurface regions.

149. The biodegradable stent prosthesis of any of clauses 130 to 148,wherein the treatment changes the shape of said structural elements toform a convex shape across the thickness of said structural elements.

150. The biodegradable stent prosthesis of any of clauses 130 to 149,wherein the treatment changes the shape of said structural elementsabluminal surface to form a substantially concave shape.

151. The biodegradable stent prosthesis of any of clauses 130 to 150,wherein the initial and patterned diameters are the same.

152. The biodegradable stent prosthesis of any of clauses 130 to 151,wherein the tubular body is formed at an initial diameter, wherein thetreatment of said structural elements does not substantially change thediameter of said tubular body.

153. The biodegradable stent prosthesis of any of clauses 130 to 152,wherein the treatment of said structural elements reduces the initialformed diameter to a smaller diameter.

154. The biodegradable stent prosthesis of any of clauses 130 to 153,wherein the treatment reduces the patterned diameter to a smallerdiameter.

155. The biodegradable stent prosthesis of any of clauses 130 to 154,wherein the treatment of said structural elements to change the width orthickness reduces an inner diameter of the prosthesis to a smallerdiameter after treatment.

156. The biodegradable stent prosthesis of any of clauses 130 to 155,wherein an inner diameter of the prosthesis after treatment is reducedby between 0.05 mm to 3 mm, preferably between 0.1 mm to 2 mm, mostpreferably between 0.1 mm and 1 mm.

157. The biodegradable stent prosthesis of any of clauses 130 to 156,wherein the treatment does not substantially change angles between saidstruts.

158. The biodegradable stent prosthesis of any of clauses 130 to 156,wherein the treatment changes at least some angles between saidstructural elements.

159. The biodegradable stent prosthesis of any of clauses 130 to 156,wherein angles between said struts changes after treatment.

160. The biodegradable stent prosthesis of any of clauses 130 to 156,wherein the angles between said struts become smaller in an amountranging from 1 degree to 75 degrees, preferably between 2 degrees 50degrees, most preferably between 2 degrees and 10 degrees.

161. The biodegradable stent prosthesis of any of clauses 130 to 156,wherein the angles between said struts become larger after treatment, inthe range of 1 degree to 75 degrees, preferably in the range of 2degrees to 50 degrees, most preferably in the range of 2 degrees to 25degrees.

162. The biodegradable stent prosthesis of any of clauses 130 to 161,wherein the treatment shrinks the length of the stent prosthesis aftertreatment.

163. The biodegradable stent prosthesis of any of clauses 130 to 162,wherein the length shrinkage ranges between 0.1 mm and 5 mm, preferablybetween 1 mm and 2 mm.

164. The biodegradable stent prosthesis of any of clauses 130 to 163,wherein the length shrinkage ranges between 1% and 20%

165. The biodegradable stent prosthesis of any of clauses 130 to 164,where the treatment comprises chemical treatment of said patterned stentwith at least one solvent.

166. The biodegradable stent prosthesis of any of clauses 130 to 165,wherein a stent prosthesis weight after removal of the at least onesolvent is substantially the same after treatment as before treatment.

167. The biodegradable stent prosthesis of any of clauses 130 to 166,wherein a coating is disposed over at least a portion of said stentprosthesis.

168. The biodegradable stent prosthesis of any of clauses 130 to 167,wherein the coating comprises a drug.

169. The biodegradable stent prosthesis of any of clauses 130 to 168,wherein the coating comprises a drug and a polymer.

170. The biodegradable stent prosthesis of any of clauses 130 to 169,wherein the coating contours to structural element outer surfaces.

171. The biodegradable stent prosthesis of any of clauses 130 to 170,wherein the coating thickness ranges between 0.5 and 10 micrometer,preferably ranges between 1 micrometer and 7 micrometer, and mostpreferably ranges between 1 micrometer and 5 micrometer.

172. The biodegradable stent prosthesis of any of clauses 130 to 170,wherein the coating does not substantially change the surface area ofthe structural elements.

173. The biodegradable stent prosthesis of any of clauses 130 to 171,wherein the coating surface area changes the surface area of thestructural element by less than 10%.

174. The biodegradable stent prosthesis of any of clauses 130 to 173,wherein the thickness of a structural element is measured between theabluminal and luminal surfaces, and the width of said structural elementis measured between the side surfaces of said structural element.

175. The biodegradable stent prosthesis of any of clauses 130 to 174,wherein the treatment comprises heating the stent prosthesis afterpatterning to a temperature ranging between 50° C. and 180° C.

176. The biodegradable stent prosthesis of any of clauses 130 to 175,wherein the treatment comprises heating the stent prosthesis afterpatterning to 30° C. to 100° C. above the Tg of said polymeric material.

177. The biodegradable stent prosthesis of any of clauses 130 to 176,wherein the heating is for a time between 1 minute and 5 hours,preferably between 5 minutes and 4 hours.

178. The biodegradable stent prosthesis of any of clauses 130 to 177,wherein the stent prosthesis is crimped to the crimped configurationhaving a smaller diameter than the initial diameter at which the stentis formed.

179. The biodegradable stent prosthesis of any of clauses 130 to 178,wherein the stent prosthesis in the expanded configuration does notfracture.

180. The biodegradable stent prosthesis of any of clauses 130 to 179,wherein patterned diameter of the stent prosthesis is 1.1-1.5 times anintended deployed diameter of the stent, and wherein the stent at theintended deployed diameter does not fracture.

181. The biodegradable stent prosthesis of any of clauses 130 to 180,wherein the polymeric material crystallinity after treatment increasesby at least 10% or by at least 20%.

182. The biodegradable stent prosthesis of any of clauses 130 to 181,wherein the polymeric material crystallinity after treatment rangesbetween 5% and 50%, preferably ranges between 5% and 30%.

183. The biodegradable stent prosthesis of any of clauses 130 to 182,wherein the elastic modulus of the stent prosthesis ranges between 0.35GPa and 1.5 GPa.

184. The biodegradable stent prosthesis of any of clauses 130 to 182,wherein the tubular body is formed from a substantially continuouspolymeric tube.

185. The biodegradable stent prosthesis of any of clauses 130 to 184,wherein the treatment is performed to change the shape of at least somestructural elements wherein said structural elements have an abluminalsurface, a luminal surface, and two side surfaces, said treatmentchanges the shape of said abluminal surfaces to a shape that issubstantially concave or convex across the width of said abluminalsurface.

186. The biodegradable stent prosthesis of any of clauses 130 to 185,wherein the treatment is performed to change the shape of at least somestructural elements wherein said treatment changes the shape of saidside surface regions from being substantially flat or straight to ashape that is convex across the sides of said structural elements.

187. The biodegradable stent prosthesis of any of clauses 130 to 186,wherein the treatment is performed to change the shape of at least somestructural elements wherein said structural elements have an abluminalsurface, a luminal surface, and two side surfaces, said treatmentchanges the shape of said abluminal surfaces and side surfaces; to abulbous shape extending between the abluminal surface region and theluminal surface region of said structural elements.

188. The biodegradable stent prosthesis of any of clauses 130 to 187,wherein the structural elements shapes are viewed and/or measured usinga cross section of said structural element, or using part or all of astructural element.

189. The biodegradable stent prosthesis of any of clauses 130 to 188,wherein the structural elements shapes are viewed and/or measured usinga using a two or three dimension viewing means.

190. The biodegradable stent prosthesis of any of clauses 130 to 189,wherein concave luminal and/or abluminal surface regions join convexside surface regions at lips which extend along at least some of thestructural elements.

191. The expandable stent prosthesis of any of clauses 130 to 190,wherein the lip forms a thickest point of the structural element crosssection.

192. The expandable stent prosthesis of any of clauses 130 to 191,wherein the lip is in the shape of a wave where the surface regionsmeet.

193. The expandable stent prosthesis of any of clauses 130 to 192,wherein the lips extend continuously along a strut and a connected crownof the expandable stent prosthesis.

194. The expandable stent prosthesis of any of clauses 130 to 193,wherein the stent prosthesis cross section has concave luminal and/orabluminal surface regions and convex side surface regions which form acontinuous curve across the side surface regions to provide a continuousconvex curve in the form of an arc which extends between abluminal andluminal lips.

195. The expandable stent prosthesis of any of clauses any of clauses130 to 194, wherein at least some abluminal surface regions and at leastsome luminal surface regions join said side surface regions at a lip anda thickness between an abluminal lip and a luminal lip forms a thickestpart of the cross section of said structural elements, while a thicknessat a core or substantially a midpoint between the abluminal lips forms athinnest part of the cross section of said structural elements.

196. The expandable stent prosthesis of any of clauses any of clauses130 to 195, wherein the structural elements prior to treatment andfollowing treatment are substantially free from pits, holes or grooves.

197. The expandable stent prosthesis of any of clauses 130 to 196,wherein the structural elements have a substantially square orrectangular cross section before treatment which becomes a non-square ornon-rectangular cross section after treatment.

198. The expandable stent prosthesis of any of clauses 130 to 197,wherein the prosthesis further comprises a metallic biodegradablematerial

199. The expandable stent prosthesis of clause 198, wherein thebiodegradable metallic material comprises metal or metal alloy.

In embodiments of the disclosure according to any of the above clauses,at least some of the stent structural elements are elongate and have asimilar cross-section along their length or at least along a majorportion of their length. In embodiments of the disclosure according toany of the above clauses, at least some of the stent structural elementshave the same cross-section along their length or at least along a majorportion of their length. The cross-sections of different stentstructural elements may be the same, similar or different.

What is claimed is:
 1. A biodegradable stent prosthesis comprising apolymeric material, said stent comprising structural elements which haveabluminal, luminal and side surface regions, said structural elementscomprising struts joined by crowns wherein at least some structuralelements have convex abluminal surface regions and substantially flat orsubstantially concave luminal surface regions, said abluminal surfaceregion having said convex surface region on said structural elements inthe absence of a coating on said structural elements, said stentprosthesis being expandable from a crimped configuration to an expandedlarger configuration and having sufficient strength in the expandedconfiguration to support a body lumen.
 2. The biodegradable stentprosthesis of claim 1, wherein the structural elements havesubstantially convex or substantially flat side surface regions.
 3. Thebiodegradable stent prosthesis of claim 2, wherein the structuralelements have a lip or a ledge between the abluminal and side surfaceregions or between the luminal and side surface regions.
 4. Thebiodegradable stent prosthesis of claim 3, wherein the lip protrudesoutwardly.
 5. The biodegradable stent prosthesis of claim 1, wherein thestructural elements are substantially smooth and substantially free fromrough edges.
 6. The biodegradable stent prosthesis of claim 1, whereinthe thickness of said structural elements is greatest near a midpointbetween the sides of said structural elements.
 7. The biodegradablestent prosthesis of claim 1, wherein the width of said structuralelements is greatest at about the center of said structural elements. 8.The biodegradable stent prosthesis of claim 1, said abluminal surfaceregion having said convex surface region on said structural elementswithout the presence of a polymeric coating on said structural elements.9. A biodegradable stent prosthesis comprising a polymeric materialwherein the stent prosthesis has been formed from a tubular body havingan initial diameter and the tubular body has been patterned into a stentwith a patterned diameter, said stent comprising structural elementswhich have abluminal, luminal, and side surface regions, said structuralelements comprising struts joined by crowns wherein said structuralelements have been treated to shape at least some structural elements tohave convex abluminal surface regions and substantially flat orsubstantially concave luminal surface regions, the weight of said stentprosthesis before said treatment and after said treatment issubstantially the same, said stent prosthesis being expandable from acrimped configuration to an expanded larger configuration and havingsufficient strength in the expanded configuration to support a bodylumen.
 10. The biodegradable stent prosthesis of claim 9, wherein thestructural elements have substantially convex or substantially flat sidesurface regions.
 11. The biodegradable stent prosthesis of claim 9,wherein the structural elements have been shaped by the treatment afterpatterning, said treating comprising one or more of chemical treatment,heating, mechanical shaping, laser shaping, or blasting.
 12. Thebiodegradable stent prosthesis of claim 11, where the treatmentcomprises chemical treatment of said patterned stent with at least onesolvent.
 13. The biodegradable stent prosthesis of claim 12, whereinsaid weight after treatment is after the removal of substantially allsolvent.
 14. The biodegradable stent prosthesis of claim 11, where thetreatment comprises chemical treatment of said patterned stent with atleast one solvent which can dissolve the polymeric material and a secondsolvent which does not substantially dissolve the polymeric material.15. The biodegradable stent prosthesis of claim 14, wherein thetreatment with the first solvent ranges from 0.5 seconds to 5 secondsand the second solvent treatment ranges from 0.5 seconds to 60 seconds.16. The biodegradable stent prosthesis of claim 14, where the treatmentwith the two solvents does not substantially dissolve the polymericmaterial.
 17. The biodegradable stent prosthesis of claim 14, wherein astent prosthesis weight after removal of the solvents is substantiallythe same after treatment as before treatment.
 18. The biodegradablestent prosthesis of claim 14, wherein the solvent treatmentredistributes the polymeric material to change the shape of at leastsome structural elements.
 19. The biodegradable stent prosthesis ofclaim 9, wherein the structural elements have an initial shape and thetreatment changes the shape of said structural elements.
 20. Theexpandable stent prosthesis of claim 19, wherein the initial shape ofsaid structural elements is substantially square or rectangular crosssection before treatment which becomes a non-square or non-rectangularcross section after treatment.
 21. The biodegradable stent prosthesis ofclaim 9, wherein the tubular body has been formed using extrusion,spraying, dipping, molding, or printing.
 22. The biodegradable stentprosthesis of claim 9, wherein the tubular body has been exposed to anadditional treatment before patterning, said additional treatmentcomprises at least one or more of heating, cooling, pressurizing thepolymeric material, or chemically treating the polymeric material. 23.The biodegradable stent prosthesis of claim 9, wherein the treatmentchanges the thickness or width of at least some of the structuralelements.
 24. The biodegradable stent prosthesis of claim 9, wherein thethickness is larger after treatment.
 25. The biodegradable stentprosthesis of claim 24, wherein the thickness changes after treatment byfrom 2 micrometer to 35 micrometer.
 26. The biodegradable stentprosthesis of claim 9, wherein the width of at least some of saidstructural elements is decreased after treatment.
 27. The biodegradablestent prosthesis of claim 26, wherein the width changes after treatmentby from 2 micrometer to 35 micrometer.
 28. The biodegradable stentprosthesis of claim 9, wherein the initial and patterned diameters arethe same.
 29. The biodegradable stent prosthesis of claim 9, wherein thetubular body is formed at an initial diameter, patterned atsubstantially at the initial diameter and the treatment of saidstructural elements after patterning does not substantially change theinitial diameter of said tubular body.
 30. The biodegradable stentprosthesis of claim 9, wherein the treatment of said structural elementsdoes not change the stent pattern or stent geometry.
 31. Thebiodegradable stent prosthesis of claim 9, wherein the stent prosthesisis heated one or more times after patterning and before crimping to atemperature ranging between 70° C. and 150° C. without substantiallychanging the pattern, diameter or geometry of the stent.
 32. Thebiodegradable stent prosthesis of claim 31, wherein the heating one ormore times after patterning is to a temperature ranging between 90° C.and 120° C.
 33. The biodegradable stent prosthesis of claim 32, whereinthe stent prosthesis is crimped to the crimped configuration having asmaller diameter than the initial diameter at which the stent is formed.34. The biodegradable stent prosthesis of claim 31, wherein the heatingis for a time between 1 minute and 5 hours.
 35. The biodegradable stentprosthesis of claim 31, wherein the polymeric material crystallinityafter heat treatment increases by at least 10% or by at least 20%. 36.The biodegradable stent prosthesis of claim 31, wherein the polymericmaterial crystallinity after heat treatment ranges between 5% and 50%.37. The biodegradable stent prosthesis of claim 9, wherein the stentprosthesis is heated after patterning to 30° C. to 100° C. above the Tgof said polymeric material.
 38. The biodegradable stent prosthesis ofclaim 37, wherein the crimping temperature is about 40° C. to about 55°C.
 39. The biodegradable stent prosthesis of claim 9, wherein patterneddiameter of the stent prosthesis is 1.1-1.5 times an intended deployeddiameter of the stent.
 40. The expandable stent prosthesis of claim 9,wherein the structural elements prior to treatment and followingtreatment are substantially free from pits, holes or grooves.
 41. Thebiodegradable stent prosthesis of claim 9, wherein said weight aftertreatment is after the removal of substantially all treatment material.42. The biodegradable stent prosthesis of claim 9, wherein said weightafter treatment is after the removal of substantially all non-polymericmaterial.
 43. The biodegradable stent prosthesis of claim 9, wherein themaximum width of at least some structural elements is smaller after saidtreatment than before said treatment.
 44. A biodegradable stentprosthesis comprising a polymeric material, said stent comprisingstructural elements which have abluminal, luminal and side surfaceregions, said structural elements comprising struts joined by crownswherein at least some structural elements have convex abluminal surfaceregions and substantially flat or concave luminal surface regions and,wherein said convex abluminal surface region has a concave sectionlocated at about the mid-point between the side surfaces, said sidesurface regions extending between the abluminal and luminal surfaceregions in a continuous convex curve or substantially flat contour, saidstent prosthesis being expandable from a crimped configuration to anexpanded larger configuration and having sufficient strength at theexpanded configuration to support a body lumen.
 45. The expandablebiodegradable stent prosthesis of claim 44 which has been formed as atubular body and patterned into a stent prosthesis.
 46. Thebiodegradable stent prosthesis of claim 45, wherein the tubular body isformed from a substantially continuous polymeric tube.
 47. Abiodegradable stent prosthesis comprising a polymeric material, saidstent comprising structural elements which have abluminal, luminal andside surface regions, said structural elements comprising struts joinedby crowns wherein at least some structural elements have convexabluminal surface regions and substantially flat or substantiallyconcave luminal surface regions, said stent having a coating whichsubstantially contours to and substantially maintains the convex shapeof the abluminal surface region of said structural elements, said stentprosthesis being expandable from a crimped configuration to an expandedlarger configuration and having sufficient strength in the expandedconfiguration to support a body lumen.
 48. The biodegradable stentprosthesis of claim 1 or 47, wherein the abluminal surface region has anindentation between the two side surface regions.
 49. The biodegradablestent prosthesis of claim 48, wherein the indentation is located atabout the mid-point between said two side surface regions.
 50. Thebiodegradable stent prosthesis of claim 49, wherein said indentationdepth ranges from 1 to 50 micrometers in size.
 51. The biodegradablestent prosthesis of claim 49, wherein greatest width of said indentationranges from 1 to 50 micrometers in size.
 52. The biodegradable stentprosthesis of claim 48, wherein the thickest portion of said structuralelements is adjacent to said indentation.
 53. The biodegradable stentprosthesis of claim 48, wherein there are two bumps along the abluminalsurface region flanking the two sides of said indentation.
 54. Thebiodegradable stent prosthesis of claim 53, wherein said bumps areasymmetrical in shape and size.
 55. The biodegradable stent prosthesisof claim 1, 44 or 47, wherein said structural elements have convex sidesurface regions.
 56. The biodegradable stent prosthesis of claim 1, 9,44, or 47, wherein the flat or concave luminal surface regions joinconvex side surface regions at one or more lips which extend along atleast some of the structural elements.
 57. The biodegradable stentprosthesis of claim 1, 9, 44 or 47, wherein the polymeric materialcomprises at least one material selected from the group consisting oflactides, poly-DL-lactide, polylactide-co-glycolide,polylactide-co-polycaprolactone, poly(L-lactide-co-trimethylenecarbonate, polyhydroxybutyrate,polyhydroxyvalerate, poly orthoesters, poly anhydrides, polylactide,polyglycolides, polycaprolactone, tryrosine derived polycarbonates,polyiminocarbonates and copolymers thereof.
 58. The biodegradable stentprosthesis of claim 1, 9, 44, or 47 wherein a coating is disposed overat least a portion of said stent prosthesis.
 59. The biodegradable stentprosthesis of claim 58, wherein the coating comprises a drug.
 60. Thebiodegradable stent prosthesis of claim 59, wherein the coating contoursto struts and/or crowns outer surfaces without substantially changingtheir shape.
 61. The biodegradable stent prosthesis of claim 58, whereinthe coating comprises a drug and a polymer.
 62. The biodegradable stentprosthesis of claim 1, 9, 44 or 47, wherein the elastic modulus of thestent prosthesis ranges between 0.35 GPa and 1.5 GPa.
 63. The expandablestent prosthesis of claim 1, 9, 44 or 47, wherein the prosthesis furthercomprises a metallic biodegradable material.
 64. The expandable stentprosthesis of claim 63, wherein the biodegradable metallic materialcomprises metal or metal alloy.
 65. The biodegradable stent prosthesisof claim 9, 44 or 47, wherein the struts and/or crowns are substantiallysmooth and substantially free from rough edges.
 66. The biodegradablestent prosthesis of claim 1 or 47, wherein said side surface regionsextend between said abluminal and luminal surface regions in acontinuous convex or substantially flat contour.
 67. The biodegradablestent prosthesis of claim 1 or 47, wherein said structural elements arestruts.
 68. The biodegradable stent prosthesis of claim 47, wherein saidcoating substantially contours to and substantially maintains the shapeof the surface regions of said structural elements.